You can ask yourself a few questions to determine if you do have a crush on this girl. Do you think about doing romantic or sexual things with this girl? Do you want to go on dates with her and kiss her? Does the thought of her dating someone else make you feel jealous? Or do you simply like spending time with her as a friend?
I'm assuming you are in high school or middle school based on your question. This can be an awkward time for many people as you are still figuring things out. Let me use a couple of examples from my past to help you figure things out.
Before I admitted to myself that I was bi, I had crushes on some girls but didn't want to admit it. In middle school, there was a girl I liked, and I thought about her as much as I did any boy I ever had a crush on. I tried to tell myself that it was just a "friend crush," not a real crush (that I just wanted to be better friends with her), even though I thought about her way more than I thought about anyone else I was just friends with.
Fast forward a few years to high school. There was a boy I was friends with and thought I had a crush on. I assumed it was a regular crush, because he was a boy. (At this point, I knew I was attracted to girls and boys, but still didn't want to admit that I was bi to anyone). Eventually, I realized that I did not have a crush on him because when I imagined kissing him, I felt kind of grossed out. It turns out I just liked hanging out with him as a friend, but did not have any romantic or sexual feelings for him. Because of the cultural narrative that any interaction between boys and girls is inherently romantic, I assumed that I must like him that way if I liked him at all, even though that turned out to not be the case. So it is possible to think you have a crush on someone, but then realize that you only really like them as a friend.
There was also another girl whom I had a crush on at this same time that I thought I had a crush on that boy, but I tried to suppress those feelings because she was a girl, even though sometimes she did seem to be interested in me, but I never trust my own gaydar, so I wasn't sure if she even liked girls, let alone me (turns out she was gay, though who knows if she ever liked me back). It's possible to have crushes on multiple people at the same time, however, in this case, I didn't like that boy in that way, even though I thought I did for a while.
Also, before I was ready to admit to myself that I am bi, I would feel kind of uncomfortable walking past ads featuring sexy women, such as the ones in front of Victoria's Secret. I was sure someone would notice me looking a little too intently at those images if I allowed myself to look at them at all, so I averted my gaze. Straight women wouldn't even think anything of it and would have no physical reaction to those types of images.
So ask yourself. Can you picture yourself in romantic situations with this girl? Or do you simply enjoy spending time with her? Do you find yourself physically attracted to girls you know or to images of sexy women in the media? Do you have the same kinds of thoughts about women that you have about men?