That sounds messed up :c
Don’t you worry, I’m completely on your side. Being tired of insults is a very possible reason but I personally think you should still ask him (Your bf) why he kicked her out.
Also, this started happening after you got a bf right? Well not to sound ridiculous but I think she has feelings for you. I think so because all her “attacks” are directed towards your bf so she may be jealous.
But even if that’s the case, it’s NOT COOL to do such things. Maybe sit down one day and have a talk with her? You may be able to cool down the situation.
Really hope this helps