best friend acting weird

Okay so, my best friend has been acting super weird lately, her and her boyfriend broke up after a year, and I understand that she is still hurt about that. She has been being very sneaky, she has been lying to me and just down right nasty. I understand friends are supposed be honest, but she is just being plain rude. I don't know what to do, should I let her treat me like this or say something? I've said things to her before but it always ends up in a huge fight, but I'm sick of being treated like this. Help?!?!