Comenten que puedo hacer me tiene loco la pendeja

Good afternoon, I have a problem my sister in law doesn't know what's going on with her the truth I don't know if it's my imagination or if it's really happening and I don't know how to approach her. I'll tell you we've been having cross-eyed glances and things like that she's caught me looking at her, looking at her ass and that and doesn't say anything and I've also seen her looking at me or looking at me provocatively, also making provocative poses in front of me. I notice when we play together her nipples get hard and I don't know if it's my imagination but I'd like to know if she wants something with me, does she want it or wants to screw? Before she wasn't like that with me. Honestly I do want to screw her whole I'm dying but I don't know how to approach her what should I do? How will I know if she's not going to do anything. I saw photos of hers in a thong and things like that (that was secretly left open on Google Photos on the PC) now I don't see her with the same eyes anymore and I think she doesn't feel the same way about me as before... Give me advice. I also don't want to screw up my relationship with my girlfriend if I tell something to my sister in law and she tells her... Another thing I give her attention in all stories and photos I always raise the bar but she doesn't say anything to my sister once I even passed a song that's called forget fear by drefquila (it says part of it forget fear, I also want to eat you, although I know I shouldn't neither did she say anything. How can I know if what I speculated is true and approach her or leave it like this. That girl has me crazy.