Girl lead me on ? Did I do the right thing ?

Good that you told her to stop but it just sounds like she's mass sending snap chats to her friends? I don't think she's still trying to flirt with you.

It could be she wasn't actually flirting with you and you misinterpreted her friendliness for flirting... reminds of this really outgoing guy with a g/f who chatted with everybody including girls. Maybe she doesn't really care which gender her friends are and just really friendly and outgoing?

I think she's quiet because she's shocked that you accused her of flirting behind her b/f's back and feels awkward. Could be that you're just bias because the girl you liked was being friendly with you and your feelings were too involved so you misinterpret every interactions with her as flirting. I don't know if its true or not though. Everyone uses snapchat. Did you give you any flirty messages? If she told you she had a b/f then I don't think she was flirting because she would have kept it a secret in the first place if she was.

There's a high chance that she wasn't actually flirting and you just misinterpreted her friendliness for something else. What kinds of things was she actually sending??