I don't think your husband needs to apologize for anything, he did what he could to give her a good life. Over and beyond what he needed to considering she is not his bio. Sounds to me your daughter needs to get over herself and apologize to him.

I think things will be ok. My DH is the only father my daughter has has since age 7. While he is affectionate with me, as far as both his own and mine, he never initiated any affection, but if and when they wanted to hug him, he obviously treasured every second of it. He just isn't a pushy, lovey dovey kind of dad. It upset me for a while, but he has been a consistent figure in her life, never questioned money, never made her feel like she did nit belong. It has not been perfect and now DD is very curious about her dad and now and then brings him up.
Maybe your daughter thinks she betrayed her dad and now has to pick an allegiance. Hopefully she will get past this and realize the value of this relationship.
As hard as it us, I would try and just be there, let her know she is entitled to her feelings, but also point out how as far as step parents, she has been very lucky. She would benefit from a lot of the conversations here, where no one is under the illusion that a step is loved unconditionally just like a biological child. What she has received may not be the entire package one hopes to get from a dad, but it is nothing to scoff at.
Be there for your husband, for whom this must be very hard.
I sure wish you the best. Hang in there. Sometimes young adults process their anger a little late and cause a lot of pain in their wake.

They say its easier to forgive a bio parent than a step parent and that a step parent is an *easier* object to blame and push all the issues on. Sounds like this is what has happened here.

Your daughter obviously missed the emotional connection between her and her SD, and at 21 is too immature and shortsighted to realise that everyone is different, that you should accept people for who they are and be grateful for the things you did receive. Her re-connection and possibly affectionate relationship with her bio dad has underlined the fact she has missed out on being "daddy's little girl" and she is left perhaps thinking there was something wrong with her, that for some reason your DH rejected her.

It seems to me he didnt. I think personally you cant force your DD to change her mind, certainly you can put your own point of view across about this and I would say I wouldnt want to hear the negative commentary regarding how your other children will fair with your DH as their dad. Personally I would say when she says things like that: "I dont think thats nice. You are forgetting who was there for you when you were younger- he didnt have to support us and provide for us. Dont blame your SD because you didnt that close father-daughter relationship,that is something you BD is to blame for - where was he? SD has been and still is good to you and you need to except that he isnt a demonstrative man or at least stop bad mouthing him. These are your issues, so own them...." then shut down any convo's going in that direction. Pointless trying to reason when she isnt prepared to listen.

I would be ashamed of her disrespect tbh and would show her this.

I feel for you and what you are dealing with right now. What IO can say is that I have 2 adult bios and 2 adult steps and ALL 4 have done the same. Even the one daughter I am closest to. I have been in counseling now for 7 months trying to deal with all of this. It is hard and it hurts like I never imagined a hurt could from a child. Infact, I have a post on here about "Why poeple feel they can tell me what you do?" explaining what I am going thru right now.

My counselor sayd that adult children reach a point in their adult years where they feel like they have taken on their adult lives and feel they have direction but really they are only trying to spread their wings and are actually very insecure. In the process they reflect on a childhood and the blame game begins. Counselor said all children come to their adult years wounded from their childhood, all have parent tapes, all feel abandoned and unloved bnut unfortunately they are the ones who have to find themselves and figure it out for themselves. We can be supportive but that we should never get into the specifics and the tit for tat stuff. She said some will hold grudges the rest of their lives and will never get past the feeling of hurt and blame for the parent. That has been terribly sad for me to realize I have poured so much of my heart and soul into my entire family and I feel I have lost them all to something that seems almost evil.

Can we say "victim mentality?"
My own daughter pulled this crap on me when she was about 20. The fact that we even have a relationship after the incredibly horrible rebellous teenage years is a miricle.
So what did I do? I did apologize to her for all of these imagined slights. But I also told her that was the last apology she would hear from me on the subject. So we've moved on.
My Dad beat the hell out of me on a regular basis and I would never in a million years have confronted him as an adult on the issue.