I wouldn't do anything. If she is trying to get between you and your boyfriend so she can have him, she isn't your friend.
A real friend wants you to be happy and if that means putting her own feelings off about YOUR boyfriend then that's what a friend does! She needs to control herself and you don't need her in your life.
I like to say "No one knows what tomorrow holds so if you can be happy today, be happy today!" I have noticed that it is when you feel the weakest, it is when you are actually the strongest. Do NOT let ANYTHING stop you from your dreams!!!! :0)
Dear May Apple,
For me the answer was YES, I did let a health scare prevent me from my goals - and every day I am glad...
The changes I made because of the health issues led me into a totally different direction in life; much more fulfilling now than what I "thought" I wanted.