I just had with my sister...?

My advise is this...your both still very young and are both in the experimental stage.Just forget what you and your sister did and suggest that she does the same as I think you know that it was wrong.It seems that you may have a liking for girls as well as men or you could just be confused because you liked the feelings her touching you gave you.Either way forget doing anything with your sister again how ever if you are interested in girls then I'm sure you will find one that is not related to you in any way.Saying all this though you are only 15 so there for you should concentrate on your school work not , don't worry the time will come when you can enjoy a relationship a time when other things are not as important.