About a crush on a girl

I’ve known her for ten years now, she’s really pretty, really nice, really smart, she’s the most perfect person I’ve ever met. That’s why I don’t want her to know just how much I love her. Because I don’t know if to her I’m just a friend, just someone she talks to, someone she likes, someone she trusts but not someone she wants anything more with. She’s my best friend and I’d do anything for her, I like to think that she would too but how am I supposed to know that? Since I switched schools, a few years ago, I send her letters on valentines day because our schools have a program to do that, in the last one I drew hearts just about everywhere because it felt right and she didn’t seem put off or anything, that’s good but, again, maybe she just sees that as normal friend stuff. In her last letter she wrote that she missed me and that we should hang out more so we made plans for this weekend and tomorrow I’m going out with her to the park and getting some ice-cream (her plan). For the last two weeks or so she’s been re-posting a lot of love-related videos and now I’m nervous as hell because she isn’t the open talk-about-everything type and I can’t help but wonder ‘is this her trying to send a signal or is she dating someone already?’ Because we have a big friend group and since we really don’t hang out all together much the posts could be about someone else. One of the posts was about the person having curly hair. Guess who has curly hair? Me and one other friend. I just don’t know what to do and don’t wanna go prodding into her life, I genuinely like her and I don’t wanna ruin our friendship or the friendship with the other friend, I feel like stalking her socials is already creepy enough and at this point I don’t know what I can/should do. My current plan is just asking in a natural-ish way about any possible relationships tomorrow and if the answer is ‘yes, I have a partner now’ then just taking some time to calm down and going back to my normal life.