Eek. I feel for you. BM was extremely HC at the beginning of our marriage. At the time, she only saw SD two weekends a month and spent all the time trying to interrogate her for information. She lacked self-esteem and confidence in being a mom.

WIth that being said though, your DH needs to stop agreeing to all of BMs empty promises. He is only setting her up for disappointment too. Also, did you say the grandpa? Did I get that right? I would NOT be arranging SKs to see other family members... not your DHs responsibility. If he wants to facilitate a relationship between SK and BM, then I would say both of them need to meet in a neutral location to ensure it happens. At least BM called! SK could have been stuck at school until 5:00 with no ride. 

Lastly, please prioritize your mental health. Even if it means taking a step back. No need to drop everything you are doing to run an outfit up to school because of BMs plans. You will exhaust yourself if you revolve your life around BM. 

First, I am very sorry for your loss. Losing a loved one can change your entire world.

(((((HUGS)))))

Is there a valid reason for her not working? If not then you are actively paying her CS for her, your contribution to her child's needs is enabling her to not work.

I don't think there is anything you can do to improve your relationship with her because she just isn't interested. I also don't think there's any point in trying to understand how she works and why she does what she does - she seems like a troubled soul to me.

My advice to keep her at arm's length or further, if possible. Remember that the only person you can change ( no matter how good your intentions) is yourself. BM has apparently decided to be miserable so ignore her as much as you can.

Yes, our late BM blamed me for everything, too.  It's so unfair and untrue.  It's hard enough being a good SM, and  I can tell you are, without BM poisoning everything.  You know she feels guilty, right?

I also feel for the girls.  Our BM didnt even have restrictions on her time with the 3 kids (just a verbal with DH).  But once they moved in full time, I dont recall any of them being with her for a weekend.  As I think back, I can recall instances with each where they tried but it never happened.  SD62 would run away when we tried to discipline her and the solution was usually to let her move back with BM, what she wanted anyway.  That woukd last a few months, then she'd be back, lather, rinse, repeat.  OSS hinted strongly he'd like to go with BM and her BF to the lake they often visited, he loves to fish.  Never happened.  YSS asked to move back with her once she and BF married (I just learned this recently).  Answer: no.  So, I feel for your girls, I kniow it's in their minds.

Some of these BMs.......

I think you may be internalizing some of this. While yes, BM has absolutely targeted you in the past, I think the issue about the dress may be misplaced.

You did not send SD to school in a nice dress because it is BM's weekend and you didn't want her to ruin it/not return it. That is a valid concern, but it is also a "pick you battles" issue. A compromise with SD could have been getting a pretty but cheap holiday dress for the occasion, so if it wasn't returned or was ruined, it's not a huge deal. But it is 100% not your fault that BM didn't get the girls. You could not have predicted it, nor could you have changed the outcome. You tried to get SD her dress and put in the effort to right the wrong. BM can try to blame you for that, but she would also have to blame herself for the fact she backed out of visitation last minute. I wouldn't internalize and talk negatively about how all of that is your fault. Lesson learned, maybe next time, have a cheap alternative for SD for these types of things if it is going to make you feel bad. 

Many of these loser BMs will blame everyone but themselves when clearly it is their fault they can't Mother. BM doesn't pay, doesn't work, and doesn't raise her kids. She can say it is your fault, but you and the world knows it's not. You are the one raising her kids, being the Mom, etc. She is going to target you because it is easier than having to self reflect and take accountability for her own crap. Let BM blow smoke, she has bigger fish to fry in her personal life and with court. 

SpermGrandHag certainly blamed my DW.  Spermidiot cheated because DW was a bad "wife".  It could not possibly have been the fault of her son who followed the cheating example set by SpermGrandPa. SpermGrandHag did not have the spine or character to kick her POS DH out shile worshipping the polluted progeny she had with her POS cheating husband allowed her to practice her self delusion.

DW never married the Spermidiot. She booted his ass out when he started cheating with yet another 16yo statutory rape victim when SS was just short of 1yo.  SpermGrandHag insisted that DW was her idiot son's wife because her fringe cult religion considered out of wedlock breeding to be apostacy.  I have no idea how she white washed her dishitiot son's repeated out of wedlock breeding career with her cult.

The Hag blamed BM then me for anything she could for the better part of 20 years. No cognition of her idiot gangbanger wannabe POS serial statutory rapist son hell bent on impregnating every accessable underage womb in the PAC NW.

We countered her crap by repeatedly beating her about the head and shoulders with a rolled up copy of the CO and with the amalgamated ever growing facts.  To minimize her manipulation of SS, we made sure that he was kept abreast of the facts in an age appropriate manner.

SS knew when the Hag was lying, manipulating, and trying to blame my DW for the shit storm hurricane that was nearly incessent in the shallow and polluted SpermClan gene pool. She truly lost her shit when SS would call her on it in real time.  The Hag would call my DW ranting and screaming about SS knowing things he shouldn't know.  DW would shut the Hag down pointing out that SS knew because she continuously lied to SS, manipulated, guilted him, and PASing him.

When the shallow and polluted end of a Skid's gene pool manipulates, counter it with the facts keeping the noses of the toxic rubbed in the stench and stains they generate in their own life's carpet. Do not let their toxic manipulation of Skids go uncountered.

IMHO of course.

Eventually, even SpermGrandHag seemingly found clarity.  SS asked me to adopt him when he was  22. We made that happen.  Some years after the adoption, after SS's three younger half sibs reached failed adulthood (Spawn #2 is a Dole Queen, Spawn #3 is a convict serving a long prison sentence, and Spawn #4 is not far behind the inmate)SpermGrandHag told SS that she was glad that he had a good man to raise him.  At that time she also told SS that his mom (my DW) was the only good person (Spermidiot) ever dated and it was too bad that #2, #3, and #4 did not also have DW as their mother.

SpermGrandHag, SpermGrandPa, and the SpermIdiot caused the shit storm of their shallow and polluted gene pool.  It took the absolute collapse of SpermGrandHag's delustions before there was any inkling of ger being at the heart of the SpermClan genetic and performance cesspool.

Facts counter the toxic morons, Keep smaking them in the face with the facts. Never stop, until they crawl under the slime covered  rock they live under at the bottom of their shallow and polluted gene pool. and stay there.  Giving Skids the facts in an age appropriate manner protects the kids from the toxic maniplations, and helps keep the toxic subdued.

In our experience at least.

You need to take a breath.  Everything will work out,  it has to.  SP unfortunately get shit apron all the time.  BM in your case does nothing except causing trouble.  When you don't take of your kids, or work, you have all this time between drugs to think about stuff.  That between drugs, BF. Not working. She could be a good mother.  
'This is the way it's going to be.  You have a long hard road. Ahead of you,   '
Even if BM lost Primary Residential,, There are thing she can still do. PTA, Classmother, events to attend.  Run around like mothers do.   She could of dressed her DD for pictures.  Not do nothing then complain 

'She chooses to do nothing but run her mouth.