weird girl keeps touching me...

i am a 14 year old girl and this little 13 year old girl keeps touching me in kinda sexual ways...idk if her touching my stomach and thighs r sexual but it makes me feel weird.. not a good weird, just a weird weird like a wtf moment. Her name is Alexa. ive known her for a while. im really good friends with her cusion Sam. so i talk to alexa alot and sit next to her on the bus alot too. everytime i sit next to her she touches my thighs.. she either grabs my thigh, place her hand on my upper thigh, or just slowly rub my whole thigh. sometimes i just igorne it, but if im talking to someone and she touches me, i turn around for a second to give her my wtf r u doing face. most of the time she igornes it. so i just start moving around on the sit so she would take her hand away, that works every time. once she went to far.. she almost touched my butt. i was talking to sam on the bus she was on the seat on the side of me. and alexa randomly placed her hand on my lower back and i felt her slowly run her hands down.. i got nervous so i jumped and move forward towards sam. sam was like "what was that?" a bump i guess..." i couldnt tell sam...alexa already gets bullied enough because shes in the dumb classes. also because shes kinda chubby.. anyway now how she touches my stomach and waist. in the bus line (we have bus lines since im still in middle school) when im talking to her she would randomly place her hand on my stomach and start slowly rubbing. most of the time i panick and do nothing but sometimes i back away and say i forgot something at my locker, and quickly walk away. when im talking to friends she would randomly hug me then start rubbing my stomach and waist with one hand. (i have lady abs idk if thats y she likes touching me) once she went way to far and almost touched my chest..i would tell u the story but i dont have enough room.Why is she doing this?Is she a lez?or a touchy person?Does she have a crush on me?-What do u think?-