Can I have a blunt conversation with a mutual friend of ours?
That depends. Why are you going to have a blunt conversation with them?
I don't appreciate the way she's treating me and I want it to stop.
I know you feel hurt by the way your friend has treated you but she may not understand why you feel hurt. Have a conversation with her, but try to be gentle about it and not so blunt. You don't want to hurt her feelings with words that are so blunt.
I won't be gentle about it. I don't care about her feelings.  Don't you see that she's making my life miserable?
I am sorry that she is making you miserable but hurting people is just going to make you feel bad. Words can be very hurtful and last a long time.