Is my decision normal? any better solution?

I am an university student. Me and my bf coupled up 10months ago. He is my first love. Before we couple up, i knew that one of my friend had a crush on him. However i knew that she is not serious about him and just wanted to toy his feelings. This is not my assumption of her character. I heard this from her own mouth. Plus, she have been trying to couple up with quite a number of guys but failed. I knew this because we used to grow in the same town and i knew her well.
After me and my bf couple up, i told her about it. She said "good... happy for u..." but then she expressed intense anger and frustration over this matter with my another friend. I overheard it. But i never do anything about it. Then when i get back home for my semester holiday, my childhood friends (Mutual friends of me and she) came and told me that she have been spreading news among my mutual friends that i cross her love life and took away her bf. She told them that my bf and her liked each other dearly and she almost propose him and i crossed their life and make everything complicated.
I was shocked to hear that. I never expect this from her. i told my bf about it and he was shocked and angry about it. Luckily some of my childhood friends still trust me. I never provoke this issue with her. But i cant talk with her as if nothing happened. Is my decision normal? recently, i get to know that she proposed another guy but he rejected her. I don't understand what is her problem? Now my university friends who were close to her have begin to avoid me. Is it something have to do with her that my university friends are avoiding me? Did she told something bad about me to them? I don't know how to figure out and solve this problem.