You are judging her by your standards - to you, a person cannot show intimacy and affection without it meaning something more.
It is not that simple, this girl views sex differently, she enjoys what she has with you, she is affectionate towards you as a friend, but she doesn't have feelings towards you that you want her to.
This has been going on a year, nothing has changed. It isn't likely to either.
Your choices:
Put up with it - you're getting sex off a girl you desire. Downside is you'll never have her and you will not be able to emotionally move on whilst this carries on. You'll never get a proper girlfriend either, you'll be in limbo and it will get you down.
Or, put a stop to it and all contact with her. You're in love with her, you cannot stay friends, it has to be a clean break. Ideal situation, she realises what she's missing, dumps her boyfriend and comes running to you!
Realistic situation, she finds another f**k buddy but tries to manipulate you with text messages about missing you yet still has her boyfriend.
Move on from her, find someone who reciprocates your feelings. This girl isn't worth it.
"Never make someone your priority, when to them you are only an option"