A question for girls?

Ok I'm not sure if this girl I like is single or not. The reason I think she isn't is because I saw her with flowers today that she got after HS graduation but I didn't see her with a guy at the graduation and she doesn't have any pictures with guys on facebook. She doesn't have her relationship status on facebook but never has and I saw pictures of her birthday party on facebook and there was no guy there who could have been her bf and she brought a guy to prom who I know she isn't dating and was grinding with a few guys (but this was about a month ago). Are flowers a common graduation gift or one that is usually only given by bfs?