So managed to finally show my DH how SD is manipulative and it's not me being crazy. 
Basically she applied false nails on herself and told SS12 they were real and not to tell DH and myself. Of course SS being SS, immediately pulled me aside as soon as we got home from picking them up and told me. I actually have no effs anymore what she does from BMs, and trained myself pretty hard to not react so I said 'oh? Why would we care?' And he shrugged and I shrugged and walked inside. He told DH and he wasn't phased either. 
 

When I went upstairs to put back DD4's clothes in her room I overheard SS speak to SD and heard him say 'Did floral speak to you? Because I spoke to Dad and they both don't mind about your nails' and she was defensive and said 'yeah I know' and he said 'so she did say something?' And SD said 'no she didn't speak to me' and he asked her 'So how do you know they don't care??' And she hesitated and blurted 'because she saw them!'

LOL I didn't. Anyway I went downstairs and spoke to DH. I asked him, why would SD lie to SS and set this charade up about her having acrylic real nails and try to hide them from us when she got here (she had her hands in her pockets). DH sighed and said he didn't know. I suggested maybe she wanted a reaction? Try to cause drama? Knowing full well we do not approve? Then saying oh they are stuck on and make me look crazy? Unfortunately for her, SS is loyal to DH so that didn't quite go to plan. 
 

DH said I hear you. It was odd and game playing but he's not reading into it and we dropped it. 

The rest of the weekend we went camping and I did very well not reacting to SD. She was getting stroppy as I pointed out to DH she hasn't showered since she got to our place and he made her shower halfway through our trip. She wore bare feet most of the trip while we were camping and wore her new Ugg boots I bought them in the creek and they got trashed. I'm chucking them out as they stink. 

When we got home she did gardening in her thongs with DH and her feet were filthy as she hasn't showered since we got home. We just got new recliners that are cream material (second hand but they are clean) and she was lying on it with her feet pressed against the side of the arm rest. Eeeek I cracked. 
I said 'oh wow dirty feet on our new lounges'. She moved her feet off and DH said  basically it was fine. I sighed and dropped it.
Later, DD found SD old notebook on her floor and there's nothing in it usually and I thought oh how odd she's using it. It's got Disney princesses on it so naturally DD picked it up. 

On the first page SD wrote a lovely piece on how nasty I was about her dirty feet on the couch and actually fabricated DH telling me off and muttering under his breath at me. I did notice her behaviour toward me after that was very 'in your face floral' thinking DH stuck up for her. I guess in her mind that's a win that's important to her, I wondered why she went to mini wife mode and was sucking up to him and helping him cook dinner. Now I know. 
 

I quietly spoke to DH and told him what I found. He was disappointed, but i explained this is why it is extremely important we be a united front. I admit my approach was narky but only because i have been keeping quiet the whole weekend and basically letting her be a disrespectful grub and that last thing with dirty feet on new lounge just basically pissed me off. If that was DD I would have been a lot firmer but I can't parent these skids.

DH apologised and said moving forward he will have my back, I think he finally got to see what I was saying for himself. Baby steps. I mentioned to SD that DD picked up her Disney princess notebook as it was lying on the floor and I put it back up for her. I could see the cogs working in her head wondering if I read what she wrote. Seriously SD if you want to vent about me on paper, don't leave it on the floor for everyone to see! At least attempt to hide it and put it away. She will know to do that next time now I guess. 

Anyway he asked the skids to shower and go to bed. SS did and of course SD didn't. She crept out of her room to sneak downstairs to grab her pjs. I was putting DD to bed and she knew I was there and still didn't shower, to make it more fun she and SS mucked around and banged furniture and giggled for an hour and DD couldn't settle. 

I just said to DH I hate the disrespect. I'm over it. SD won't ever like me that's fine. But she does need to respect our rules.

OH and another eye opener for DH was he cooked dinner and SS asked what they have to do to get out of cleaning up. Now cleaning up is grabbing the plates, rinsing and stacking them in a pile. DH explained he cooked and all he asks is his older 12 and 10 year old help him out by tidying up, while his pregnant wife cleans our 4 and 1 year old and get them into bed. But they find this task difficult and can't understand why they have to do it. At BM's they don't do any chores. Again they don't understand respect. DH got pissed off but they didn't seem to notice or if they did, they didn't seem to care.