Happy Birthay to you, Juju!
I saw some problems here.
First, you have a "very ex- friend". And you do not want her to be in your birthday party, which means the friendship is not worth saving.
Second " she stole all of my friends which she met on my birthday." which means all you invited friends went to talk to her and neglected you.
If I am correct.
To me, once friend, always friend...no matter how we fight with each other. We have ways to say sorry and to keep the relatioship. And the friendship goes deeper. Why, if anyone I consider as my friend, she or he must be very kind, and reasonable,and share the same value. They are not only kind to me, but to others too, esp to someone whom I don't like. So I think that your ex friend probably was not your friend at all at first place.
And your invited friends...did they know clearly that they were there to celebrate your birthday? or to chat with someone you don't like? If they chose to go with her, do you still consider them to be your friends? If they were not considerate of your feelings?
You want to be close to good, kind, considerate people. I would rather stay away alone...or feel lonely then have some one ruin my spirit and life.
How do you define friendship?
Happy Birthday again and have fun with life.