“Sister in Law” respecting marriage?

I’m having an issue here debating where to draw the line. My brother in laws girlfriend (I put sister in law just for ease of understanding the relationship, but they aren’t married) is constantly causing issues in our family. My in laws aren’t fans of her because of problems she has caused, etc. She is constantly complaining and seeking attention, etc. Just not a super great person to be around, and most everyone knows it. I try and keep my distance. Recently, she has started messaging my husband every time she is upset about something. Every time her and my brother in law fight, she messages him, every time she is upset with her job, she messages him. A month ago, my husband attempted to block her number while we were on vacation for our anniversary so we could enjoy in peace and she came unglued and sent us messages on all social media asking why she was “being punished” and it wasn’t fair because they are family and we needed to stop “pushing everyone away”. She then target me and told me I was being controlling and making my husband avoid her and called me all kinds of names. My husband didn’t reply for a few days but eventually my brother in law told my husband it really hurt her feelings and basically shamed him into unblocking her number. So she’s back to messaging him all the time again- but she never apologized to me or anything. My husband doesn’t reply half the time, but when he does, he does so to be nice. Which I get to a degree (keep the peace). Im having a hard time though because we don’t want to cause drama, (especially because there is a family wedding coming up soon and I’m cringing thinking about how tense it would be if we tried to delete her), but at the same time it’s getting to a point where she is messaging him several times a day. Even yesterday on Mother’s Day! I can’t just enjoy my own husband anymore. Help.