How much time goes by until you become stuck in the friend zone with a girl?

I've know a girl for a month now and still haven't asked her yet because I can't quite tell if she wants me to ask her out or even likes me. It's been a slow process but one night a couple of weeks ago she stayed up talking with me until 5 a.m in the lobby of my dorm floor and I felt like I should have done it then. I am worried I am missing my chance because it feels like I should ask her out in the next week or forever hold my peace so to speak and forever be her friend. On top of that we have a ton of mutual friends like 10 to 15 we are really close with and we live in the same dorm building. Any advice? thank you