Secretly dating my cousin

I live in MEna Arkansas, and im a 15 year old guy. I have a girlfriend named Jennifer at my school here. But last weekend I went to my grandmas at Hot Springs and my 15 year old cousin, Katia, was there. SHe has a boyfriend in her school at Bryant. But we discovered that we have feelings for each other. She is insanely cute, and she’s my first cousin, but not by blood. She was adopted from Ukraine by my aunt, so we’re not blood related, but we’ve known each other all our lives. Saturday night we made out, and I just love her as my secret girlfriend. WHat do you guys think? I love Jennifer a lot, obviously, but I also have feelings for Katia too.