Idk what to do with this girl

Me and this girl (girl #1) have been talking and hanging out but I don't really see it going anywhere. She knows I like her but I'm pretty sure she only sees us as friends either way. I feel like she kind of get jealous when she finds out Im talking or If I hang out with other girls but I also get kind of jealous when she does the same. She has a sister that is actually a year older then me who when the 3 of us hang out together I find it more fun being around her sister. We talk way more then me and girl #1. I lowkey been developing a crush on her sister but bearly talk to her sister since I don't see her much and don't have her number or anything. should I ask girl #1 for help? I feel like it would be a bit awkward but what do you guys think?