How do I know if I’m gay?

I (15, f) recently broke up with my boyfriend, and one of my guy friends is trying to set me up with one of his friends, who is gay. However, I’m not 100% sure about my own sexuality. I’ve dated a girl before, and at one point, I think I did like her, but I lost feelings when she started ghosting me. Even though we dated for almost a year, I had no trouble breaking up with her so I don’t know if I really did have feelings. Other than that, I’ve only been interested in boys. My ex-girlfriend and I did kiss, and I did like it, but I’m not sure if that makes me gay. I’ve also had a bit of a crush on my best friend, but I’m not sure if it’s just a "friend crush" or something more.