what should I do? am I bi? or is she taking advantage of me?

ok so my brother is 16 and he has an ex girlfriend her name is joanna and shes goth, and 16 too and shes bi, and im 13, and not really goth but lets just say joanna has put a big influence on me. so anyway, I think of joanna a lot…like kissing her and stuff and touching her

so one night, I was staring at joanna because we were only in bras and thongs and I started kissing her, but she pushed me away and said, “lori!” and pushed me away lighting and I kept saying sorry sorry but she just grabbed me and was kissing me furociously and she was touching my boobs, and than I pushed her back but than I started kissing her again than she laid me on the bed and she was leading her hand down inbetween my legs and rubbing me very intensley but I pushed her back again and she said, “I thought you wanted me to” and I said, “yea but I dunno” and she was leaving but I grabbed her back into bed and I let her touch me and she humped on me and we took a video and watched it in the morning and while watching the video she was making out with me and touching me more, like she was doing eevrything I wasnt doing anything, she was just rubbing her leg on me and licking me and she would kiss me really deeply with her tongue and she would have me hump on her so that I have “pleasure” as she would say and she always rubbs her legs on me and than after I hump on her she humps on me and makes these loud moaning sounds while on me and I always try to pull her away but than I say no wait I like it,

so I was just wondering, is she just using me as a sex toy, or am I really bi? because I really really like her and I was the one who started on her