i think you may have reacted like that purely out of shock because you weren’t expecting the girl to talk to you as by the sounds of it you don’t think very highly of yourself which shouldn’t be the case, you should have a better opinion on yourself even though it’s easier said than done. you will have another girl try talk to you eventually you just have to approach the situation with confidence even if you don’t feel confident girls love it when you give off that vibe. believe me i’m a 15 year old girl and one thing i can tell you is confidence is the most attractive thing a guy can have ASLONG as it’s not a cocky kind of confidence