I'm wondering if what this is really about is that you were the one who got your daughter into basketball on your own. There's a good chance your ex feels, at some level. that you should have talked to her about the basketball thing first rather than just signing the kid up and telling you after the fact.-that, while it was not your intent to exclude, that you may simply have assumed she would be fine with this, she needed to feel that you were showing her the respect of discussing this with her rather than, as she may have seen it, deciding the whole thing on your own.

(It is very telling that you put the letter-word "I" in quotes when referring to your role in this)

If that is the case, I think what could be happening here is that she has chosen to express her frustration at being, as she could have seen it, blindsided and left out of the role she should have had in deciding this- not by expressing her anger or frustration to you directly, but by punishing you indirectly and your daughter directly, even though the child was not the one who chose to bring her into the conversation, by making it impossible for your daughter to enjoy the experience.

I suggest you call your wife and ask her if she feels she didn't have her share of the say in this, and if what she is feeling is disrespect at you. If she says yes, you will need to apologize for not recognizing that you should have discussed this with her first, and then tell her to express her anger towards you, rather than doing what she seems to be doing, which is taking something out on your daughter that the kid is not in any way responsible for- that she needs to express this to YOU, since you are the one she clearly has the issue with- and it may be an issue about more than just this one decision, but about a general problem with communications between the two of you.

I'd also suggest you say to your ex that it's fine for her to offer to practice with your daughter and offer her positive tips on the game- but she needs to back off during the team practices and that she is only going to undermine your daughter's chances of fitting in with and staying on the team if she keeps acting like she does in THOSE situations

(on edit) and on further reflection, I'd say you need to make a firm stand about telling your ex-wife NOT to make your daughter play against .yobur ex's 6'3' boyfriend- no child is going to learn anything about a sport by being forced to play against a large, possibly intimidating-looking grown-up.