At 28, why does she have access to Dad's Amazon account? Why would she assume Dad come shovel her driveway?

Doesn't sound like you're the one who needs to disengage. It's Daddy. He's raised a nonfunctional baby.

Too bad that it has to come to this but you are being used by both DH and SD as a whipping post. They have both failed to take responsibility for their actions and weaknesses so you are very convenient to blame when SD does not have the courage to address the real problems she is having with the failure of her parents' marriage or when DH does not have the courage to insist SD respect you as his wife. You have to disengage for your own emotional survival.

When you disengage you allow your DH to handle everything with SD. This means she does not take up any emotional space in your brain. Try to refrain from having any conversations with DH about SD. If your DH relays any dealings he has with SD or tells you she is blaming you, just say, "Hmmm, don't know anything about it. You'll have to discuss it with her", and leave. If she comes over for the holidays ignore, ignore, ignore. If she makes any demands of you simply say, "You'll have to talk to your Father." This forces SD and DH to communicate with each other - something that should have taken place a long time ago.

Don't be surprised to find that SD shuns DH and DH gets more frustrated. At this time is is hard not to feel sorry for DH but remember - he did it to himself.

Your husband IS the problem, not the SD, who just does what she is allowed to do without question by your husband. You are not alone here. You need to protect yourself because you cannot count on him to protect you. Every time she says something unpleasant to insult you directly, call her out. Ignore her otherwise until her behavior improves or she stays away from you altogether.

Disengaging is not easy and it is a last resort when you have a husband who is a dadeeee doormat to grown people.

As I have learned recently through my therapist, there is disengaging and there is passive aggressive disengaging. Turns out I have been doing passive aggressive disengaging for years which has helped me somewhat but not nearly enough had I been actually disengaged Only get involves if it affect you directly, otherwise, just remember, she doesn't exist and means nothing to you. Good luck!

If, after all these years, why would you permit her to ruin another holiday? Of course, she's not coming your holiday party. Why would invite someone who is rude and disrespectful? If he wants to see her at some point over the holidays, great. But you shouldn't be her punching bag. And it's too bad he didn't speak up. That's so cowardly. Change the Amazon account yesterday. As for the family rift, there's already one and that's the elephant in the room everyone pretends isn't there but they all know is. So the rift is already there. If anyone asks (and they will), simply say, that plans changed. Everyone will know. I feel for you. Wish you weren't going through this. Hope you're able to stand up for yourself so you don't spend one more holiday in misery. Remember, by continuing the cycle, you're enabling her bad behavior. It ends when you decide it ends. At least in your house.

I did not invite my SS and his GF to the Christmas dinner I had for DH's family last year. DH pouted for a couple of days after I told him they were not invited. But he got over it. No one else cared.

I would do what ybarra suggested in the first response to the OP. No way you have to put up with any s**t from a 28 yr old!

Don't disengage. IMHO disengaging gives the partner a get out of jail free card in dealing with their toxic spawn. You handled this well. Informing DH that you would call her out on any crap was exactly the right message IMHO.

Keep DH clear on that message and let him know that SD will get shredded if she steps out of line and if he wants to prevent that then he needs to keep a very focused hairy eyeball on her every second she is there.