Just go over to her house, you and her, and just have a quiet face-to-face conversation and if she interrupts what you have to say, just tell her, shhh, I need you to listen for a bit, and calmly but bluntly vent your frustrations and how you feel. Then when you finish, she can vent her side. Basically this is a woman-to-woman conversation that needs to take place.
Tell her if her behavior does not improve you will no longer be going over to her house for family functions b/c the environment is difficult for you to communicate in.
You've done all you can do, put that ball back in her court and make her do something about it!
