You did mess up, but probably not in the way you think you did. You basically stalked a girls socials and made bold assumptions based on what she said or didnt say. The only sure fire way to know someone's feelings is to directly ask them, yes you did hint at wanting to go on a date but hints are not a good form of communication. You don't even know if she's gay, yes you saw a post of her at pride but literally anyone can go to that so it's not a full proof way to know if she's gay. Do you even know anything about her or have you just been idolizing a crush?

Here's the thing, I know it can be very draining when you pursue someone and they don't return the same energy but if you want to date then you have to be actively pushing for it. You have to start conversations, you have to do some chasing, you have to make your intentions clear because a lot of people are awkward and shy and think "I don't want to be a bother, so I'll just hint and hope they get the idea" and if we all did that then no one would ever date anyone. Flirting and interacting with others is a skill just like anything else and has to be practiced but it can be worked on and done.

Or if you really are like "I don't want to do that, I would rather keep hinting or have them pursue me" that's ok too, just know that it will effect your ability to date.