Which one should I choose?

Hi!

Recently, I really liked this girl. Over 5 months I tried to get closer to her. I have told her I liked her just 2 weeks ago. I thought she liked me and she said that she used to really like me and now she likes someone else. She said that she still really likes me and if we don’t have a relationship now, doesn’t mean that we won’t later in life. Even after school. We are in Year 10 in school, so we are both 15. She is the first person I really liked. However, there is this other girl that really likes me. At least from what she has told my best friend. My question is which one should I choose? I really do like the first girl, but I feel like the second girl really deserves a chance. She is new to relationships so it would just be an experience for her. The thing is I am scared that if I choose the second girl over the first one then if the first one finds out that I don’t like her anymore, I don’t know how she might react. She might be annoyed at me and then I feel like I would lose the second one in the process. However, I feel that I do slightly like the second girl and I really want to give her a chance (not a relationship but just to get to know each other). Which one should I choose? Should I choose using my heart or brain? I know the first one I could lose way easier. It’s difficult. Please help.