We picked up my dsc on Friday night, and shortly after we got home 11 yo dsd (A) told us that she had forgotten some homework at bm's house. It needs to be complete by tomorrow, and they go back this evening at 6. We had already-existing plans for this weekend - we were going to be going to my il's house with bil/sil and their kids for a Labor Day get together on Sunday. My oldest dss (D, nearly 13) doesn't come for overnight visitation right now, but we had arranged with bm to pick him up Sunday afternoon so that he could come see everyone for a few hours.
A wanted her homework Saturday, but we told her that we weren't going to make an extra trip back to bm's house (it's about 30 minutes away) and said that we would pick it up for her on Sunday when we were there for D. She wasn't thrilled with having to do it on Monday, but said okay. Saturday morning we sent bm an email letting her know and asking her to have the homework ready the next day.
She bluntly said that A should come with us to get her homework herself. We wrote her back and asked her if she was saying that if we didn't have A with us, she wouldn't give us the homework. We also added that she was likely going to be with her cousins that afternoon (on days that we go to my il's, she just goes home with them after church instead of us and we meet her there later on - it's not a big deal). Bm wrote back and said no, she wasn't saying that, but that was she saying a middle schooler should be responsible for her homework and she added a snarky, "Are you saying that playing with her cousins is more important than her schoolwork?"

Here we go again.
We simply say that she rarely gets to see her cousins (which is true) and that we had been planning to be at the house anyway. We really didn't see the big deal. We also asked again whether she would give us the homework or not if A wasn't with us, as we hadn't gotten a direct answer. We also asked her to please stop picking fights with us over things like this, because it really only affects the children negatively. (She's interpreted that to be us "being rather mean" -

.)
She dramatically writes back, "Clearly you DO think her cousins are more important than her schoolwork. I'll send it with D." We calmly let her know that if that were the case, we wouldn't have emailed her about it in the first place and thanked her. There was a little more to the conversation after that and it devolved into her (probably drunkenly) asking if we knew how to work a washing machine and calling us irresponsible over visitation weekends that were missed almost a year ago due to dh's work schedule. None of that is relevant to the issue I'm asking about though, so I'll save that for another time.
On Sunday, we dropped the other kids off at my il's before we went to pick up D. A was already at my il's as predicted. We elected not to take the other kids to get D because a) they also wanted to play with their cousins and b) we weren't sure if the youngest would be sad to stop by the house and not be able to stay. My il's were fine with keeping them there. We told everyone where we were going - my fil, A and her cousin were on the golf cart and we chatted briefly with them before heading out. A said nothing about coming with us and was actually impatient to start their golf cart ride with Papa.

(Relevant, because we're also being accused of "not letting" A come with us

). We get to bm's and she acted like nothing happened, but gave us the folder.
Today, she is *still* complaining about this schoolwork thing. We really don't understand it.

She didn't say, "I would really prefer that A come get it herself as I don't know what homework it is." She didn't say, "I'm really not willing to dig through her bag to get it for her." We didn't make an extra trip just for the homework. We asked if we could grab it while we were there, since it was a simple mistake on A's part (she's always done well in school and is good about completing her work). She didn't have a discussion with us about whether or not A should lose time with her cousins as a 'punishment' of sorts. She sent a snarky reply to a simple question, and then got on the offensive about how we must think her cousins are more important than her schoolwork.
She's bitter at the world. She's still not over the divorce and she complains about dh on a daily basis to anyone who'll listen. She'll be passive aggressive and pick stupid fights because she thinks she's going to stick it to us by doing so. She's mad at my il's and bil/sil because they don't talk to her anymore and it's obviously because of dh and I (in reality, it has nothing to do with us and everything to do with the fact that she lied to dh's family for over a year post-divorce and none of them have really appreciated being manipulated and lied to - she also stopped speaking to them when they got into contact with us again). This is totally and utterly about her personal issues with our family, IMO, and the fact that she is totally miserable. I also suspect that she had been drinking last night and that contributed to how she handled herself.
Like I've said about others' exes or dh's exes, personal feelings are fine. She's welcome to process them at whatever pace she feels she needs to. She's entitled to her feelings and opinions. I'm just getting *really* tired of her dealing with them in ways that only end up putting stress on the kids.