Why does this girl do this what should i do?

hi, there is this really good friend of mine and i have liked her for a 2 years and finally got the to tell her that i liked her over the summer and when i told her she took it normally and said she knew and we went on with our life's and then a week later she told me that she liked me in front one of her friends and so we started talking and stuff and she said that she loved me and i told her the same back and so we continued talking and didn't want to ask her out till school so i waited a month since she told me we went to busch gardens and stuff and hanged out and talked and it was going really good. and then when school started i noticed that her and i started talking less cause didn't have any cles together and so i tried my best to talk to her and one day when shouldn't make it to busch i went with a bunch of other friends and we were hanging out and i notice that they started telling me that what she did to me is wrong and that i should just leave her and stuff like that and i had no idea what they were talking about and so i find out that another guy was trying to get with her and that she was trying to get with him. didn't make Sense to me because she and i were still talking and still liked each other and so i trusted her and i waited a week to see if she would tell me about her and the guy and didn't. i also found out that the guy had later on told her that didn't like her and so the next week i went to her and asked her about him and her and she said its none of my business and that she doesn't need this bullshit from me and so i tell im sorry for asking but i just wanted to know and so she got mad and i left her alone and then later on that week i go back to her and told her sorry for coming to her and acting like that and the only reason i was a little mad was because many people before have told me ill get cheated on and stuff and any girl who likes you will find a better one and so she started crying and said sorry and so life went on from there we stayed best friends and nothing really happen, and her and the guy only went out for a week and she was all sad after wards and i tried being there for her when she was all sad and then nothing about about for a week. and this all took place within one month of school starting haha. and so i eventually stopped talking to her to show her that i have my own life and that i can go get other girls and so i live and partied and so now in november she and another good friend of mine started going out and so they have been going out and whenever i p her in the hall way she will always give me this weird flirty look and smile to me (not know if she is flirting) and she gives me hugs and so for the past few weeks she has been telling me that she loves me and stuff and i never say it back because she has a boyfriend and i know she isn'tt saying it like she would say it to her boyfriend but why would she say it all of a sudden? and so today i was getting on the bus and her and her boyfriend are getting on another bus and i caught her attention and just waved hi and so she get me to open up my window and tells me that she would like me to know that she loves me and i said it back just to get it over with and she says it in front of her boyfriend which if i was him would kinda be mad over it but anyways then to lossen up the awkwardness for me i tell her boyfriend (who is my homeboy) that i love him as a JOKE! haha ok i dont know what the situation is here can someone explain whats happening and what i should do ? thanks for helping :) and sorry for the long *** thing haha