You are doing the right thing as part of disengaging from SD.   Ceasing thoughtful gift-giving is just the beginning.  Trust me, it's a bit strange at first but you will enjoy it as you get used to it!

After spending so many years trying to be thoughtful, considerate and generous - wracking your brain for the "right" gift - it's very liberating to stop doing it.  You are right that SD won't care that you don't give her anything, because she never cared when you DID.  

Take the money you would have spent on her and give it to a charity or buy something unexpected for someone else in your life.  Even if it's a few flowers for an elderly neighbor, pick up a lunch tab for a friend, etc.  When you do so, imagine in your mind the joy you will bring that person(s) instead of wasting your time, money and energy on SD.

As for your DH, tell him that it's time he takes over birthday gifts, planning etc. for his daughter as he knows her better than you, and you are sure he will find pleasure in doing so.  (ha ha ha!)  When I told this to my SO, the only thing he can think of is to write a check - so be it.  It's out of his account and I'm out of the mess.  

I used to put so much into presents for the SD's and the sgkids, only to hear them tell someone else "it was a gift from my dad." OSD told DH that she did not need to give me credit, because everyone knows that the woman picks out the presents. Dumb excuse, OSD.

Don't be surprised if your SD notices and now wants to show daddy how nice she is by being inclusive. I have not bought presents for almost 3 years now. The thoughtful expensive presents are gone, replaced by Walmart gift cards that DH purchases. The funny thing is I am now included on the thankyou notes, for presents I had nothing to do with! It makes me laugh.

You definitely at this point should remove yourself from the gift buying process and let your DH handle it by himself.

I gave up buying the SDs birthday presents a few years ago - the last thing I bought was a necklace for SD23's 18th birthday. They never got me anything for my birthday, not even a card.  I'd just had enough.  Like SacrificialLamb, I noticed that since then, they have started to get me something - they actually gave me a bottle of whisky on my 60th birthday last year which was the first time they'd ever bought me a present.  Whether they are now trying to show me up for not getting them anything I neither know nor care one jot.  I will let DH do all that from now on, I will deign to sign the card but that's it. 

LOL LOL  It can get a little amusing when DHs realize they actually have to DO something for Birthdays and holidays and you will not longer be there to save them.  Sometimes DH's even get angry about it and we have to remind them that good relationships are built on mutual respect and giving.  I never received acknowledgement for my birthday either - but judging from the few Christmas presents I DID get, I think I was lucky.

After noticing that skids completely ignored me at Christmas but wait until I'm busy to sneak a gift to their Dad (again), it is no longer my problem to buy gifts for children who have some sort of manipulative agenda. Unfortunately what they forgot in their mastermind plan is that I am the one who buys gifts and makes their day special with balloons and cake plus remind SO of their birthdays as he is notorious for forgetting... which he did.

I say good for you, you can only bang your head against a wall so many times before you have enough.

When I disengaged, I stopped reminding my DH when it was a skid birthday. After 3 YEARS, he still forgets and ends up contacting his kids/skids DAYS after the actual birthday. LMAO!

it took me years to give up on gifts.  I never got an acknowledgement let alone a thank you. When my mother came to live with us in the last years of her life, DH asked her to make a quilt for his grandson.  It was gorgeous.  I packed it up beautifully and shipped it to SD. I did not expect an acknowledgement for me, but when my 87 year old mom heard nothing, I was done.

walk away from this selfish behavior 

Yes, he was embarrassed- but not enough to call her on it!

That's great, Lisa. Now you can use that money to go buy yourself something really nice. You deserve it!