I think the main issue is that it's become an unspoken battle of wills. You keep referring about her 'dictating', you say it's your OH who insists that you go, why to prove a point?
Indeed, at the moment, the power, if there is such a thing, is in her hands, but that doesn't mean that this is what she wants. Her not coming any longer has probably been coming for quite some time, it's just that your OH and maybe you or not have not seen it coming. Your SD is probably emotionally torn part, one minute still wanting to try to rebuild her relationship with her dad, and the other minute, when once again he acts by showing that it's all of you or nothing, she just reacts by wanting nothing to do with him.
I don't think you are doing anything wrong, it's your OH who is by still trying to hang on to his perfect family where you adore his DD and she adores you and your son. By hanging on to what suits him, he is about to lose his DD for some time if not for good. She's sending his signals and he is refusing to see them. In the end, he will probably be more hurt of losing touch with her than she will be.
That example of you talking about how her dad would love to come to see her performance probably came across as accusatory and trying to make her feel guilty. This is exactly what my ex and his partner did with my DS. It was all those little things said that made him feel bad about himself and why for at least 12 months, he continued to go there although he hated going. I could see the pattern of him getting more grumpy as the week-ends came about, but didn't put two and two together. It's actually this feeling that he was made to feel guilty for how he felt that made him to decide to cut all contact. When he did, he became so much happier again, it was as if a large weight had been taken off his shoulders. It was a huge relief for him.
t's really interesting to read everyone's perspectives. Some people saying she has to respect us all and others that it's fine to not want me around and it's about her and my husband and son
There is no right or wrong views, it's about the outcome of these perspectives. If your OH wants to stick to the attitude that it's him with you and DS or nothing, then he has to be prepared that she will opt for nothing. If he is fine with losing his DD because he wasn't prepared to try to listen to what she might want rather than what he wants, than that's his choice of course.