Is my friend "acting up" because i don't go to her birthday parties? She's 27...?

There is no reason for you to keep this friendship going. When your mom gets out of the hospital, you should visit this so-called friend and go over what you describe here. She owes you an apology, and if she doesn't offer one right away, leave. Block her from texting you or e-mailing you. Take her off your Facebook page.