Ok, but not with flowers. You don’t buy flowers for someone who you met for 15 minutes whose name you don’t know on the off chance that you’ll run in to her again at the bus stop. It’s too intense and might intimidate her.
As I said, it’s a matter of degree; swinging by the area and hanging out for 5-10 minutes on the way home once or twice is one thing. Hanging around for an hour every day is another.
If, by chance, you (or the OP, rather) meet up with her again, get her name and agree to meet up for coffee or something, then by all means buy flowers for the first date and claim a belated Valentines Day. That’s cute and perfectly acceptable.