Hi guys, I could use some unbiased 3rd party/strictly etiquette opinions on a dilemma I have so I'm hoping you can help. This might be a little long, so apoligies in advance.
I have a group of 2nd cousins who are sisters (all adults in their 40's-50's). We're fairly close to this family, and closer to them than some of my first cousins. The issue is with one of the sisters.
All but one is wonderful. The one who isn't is one of those people who is socially ignorant, and you never know what she's going to say or do. She's not always nice, and more often than not she's completely obnoxious. We don't like being around her all that much, but she's family, so we deal with her at family functions and such. At times her sisters have had issues with her as well and as a result she is on and off with being on speaking terms with them and other family members.
We were initially planning on inviting all of the sisters and their spouses. But my own sister got married earlier this year in a destination wedding, and this cousin sent her back the rudest RSVP card I've ever seen. On it, she checked the line next to "decline with regret" and crossed out the words "with regret". Then, she hand wrote this:
"not with regret but because we are poor. Not everyone can pick up and fly to *city*. Have fun with the ELITE"
Here's the jist of it-we don't like this cousin. My FI doesn't want to invite her. My immediate family doesn't like this cousin, and would not be upset if we didn't invite her to the wedding. We don't want to invite her to the wedding b/c she's an obnoxious brat who we'd have to warn the DJ about in advance about grabbing the mic and causing a scene. But it feels a little squicky to me to invite the rest of her sisters, and not her. Even if they're not really close or even on speaking terms with her when the wedding rolls around.
I'm not clear on what is the right thing to do here. If we don't invite her, will I feel badly about it and regret it later? She will surely not let it go, but I'm not sure that I care. We're not close and I have no desire to be. But it'll be a pretty public slight, I think. If we do invite her, she'll likely be an obnoxious twat all night and probably start trouble with my mother and sister.
I just don't know what to do.
Is there any etiquette reason why we should invite her?