I've found whether you are direct or indirect you will need to be on your toes to keep their attention. You have to try your best to ignore the girl's uncertainty about you and plough on with the interaction.

Like bushido suggests, move the conversation onto something else that relates itself to your interest in the girl, i.e. where she is from. Remember not to just ask stuff about her though, tell her stuff about you too, i.e. what you are up to that day.