My "best friend" is spreading rumours about me!?

At school we didn't have a lesson so we were sat in the school library doing work. She got bored so we left. We sat down somewhere and I was very tired (I have anaemia who makes me have hardly any energy). She decides she wants to go and leave so we get up and start walking. I'm not as bouncy as she wants me to be so she tells me to "cheer up!" And starts walking off fast in a mood expecting me to go and run after her. I didn't because why should I? Instead I went in the opposite direction and done work somewhere. At the end of the day I found her to give her her bus fair. She tells everyone not to talk to me & someone says she called me a "b*tch" so I storm off. When I find our bus she puts her legs up so I can't sit with her. I sit alone & listen to music. Everyone was starring at me & I didn't know why. Then people were asking me if I'm a lesbian & came onto her. I was like WTF no and she started laughing. Now I'm scared to get on the bus because of what people think! What do I do?