It is a possibilty she's got a boyfriend , If so back away. It's not right and you're putting yourself at risk.
I know if ever found out I was being two timed, I would quite literally lose the plot. You don't need a beating over some girl.

On the other hand the girl could have confidence issues and needs to be nurtured more., patience mifght be th4e best solution...How long have you been texting/emailing?