Can I tell my husbands brothers gf to stop messaging him?
Why? Do you have a problem with her?
She keeps bothering him with tons of messages and i'm sick of it.
Well it would be rude to tell her that. But she also need to know her actions are causing problems.
I am going to tell her we need to see less of her.
Maybe you should let her partner know. It will be better coming form him.