So, this is a girl you rarely talked to after you switched tables and now, nearly a year later you are still obsessing over her?
Nothing. You don't say exactly how long it has been, but I will guess that you just started community college this year. Even so, it has been nearly a year since you've spoken to her with any regularity. Let this one go. In fact, the way you describe everything, there is a decent chance she would not even remember you if you ran into her somewhere.
Do I tell my friend that I have a crush on her
He has probably figured that out if you have asked him repeatedly if he talks to her. (What does he say when you have asked?)
Should I attend some events at my old high school that are open to everyone to see if she is there?
Nothing wrong with that. And if you do happen to bump into her, there is nothing wrong with striking up a conversation. It may lead somewhere. It may not. Just don't be weird about it. ("Hey there Kim, did you know I've have a crush on you like since forever?" would not be part of any conversation.)
Bottom line, you may never "bump" into her. And even if you had a phone number, it would just be way too creepy to call her based on a couple weeks of sitting next to each other in class and a few "hellos" after that.
Let this one go. It was a crush that you did not act upon at the time. Happens to most of us.