I have a step sister that i like?

i am 20 now and she will be 17 it all started when i was 15 and she was 12, she use to come on to me and i allways pushed her away and told her to leave me alone and then a year went by and we started doing morethings such as makin out and she let me finger her, also eat her out which i loved, then after like 2 years off all of this it was my birthday and she wanted to talk to me but i told her no and she was writing me letters and sliding them under my door to read and id write bk and slide them out and i told her i dont wana see her so she went and told her mom alot of stuff about what we did, i denied it all and we all argured for a couple of days but then we were fine they just disreguarded everything and away we ewnt well i didnt tal to my step sister for a lil there then she kept begging me to tlk to her and do stuff and we did fo a lil just small things like kiss and feelup, then she started hating me and not taling to me just like what i had did to her and she did this for a while so i did all kinds of stuff to get her to like me i drover her to her friends all of the time, picked her up from school and even bought her food all the time just so shed talk to me, then she started doing stuff again not like kissing or anything shed let me beat off to her while shed bend over on the couch and sometimes shed do it with out nderwear and stuff and it was better but i wouldnt touch her and she wouldnt touch me, this lasted a while, and i bought he some vibrators shed use sometimes while we did that, but she hasnt done it now in like 5 months i use to pay her to do it also sometimes with food and then shed ask for money untill i was giving her 150 at times, now my whole question is..well idk is this bad, illegal what, and what can i do to get her to like me or what i want her so damn bad all i thnk about is her all of the time,