When a girl says hmm in a text, it can mean they are considering what you said. It could also be that she is thinking of how to word her response. If she doesn't respond for too long, then she may not want to continue the conversation. It's hard to tell if someone is interested or just being polite when they say hmm in a text message because there are so many possible meanings behind it. Girls like guys who take initiative and ask them out on dates - don't wait for her to make all the first moves! When girls say "hmm" in texts, they usually have no idea what they want or need from their relationships with men.