You haven’t met in real life amd have been only talking for what a month? There is no hot or cold. She changed her mind and doesn’t want to talk anymore: busy, not up to it right now, interested in someone else instead, bad timing, doesn’t want to be talking to guys right now. It doesn’t matter why. It’s not like you are married and your spouse decided to not talk to you out of a blue.

You just have to let it go. Continue pursuing her despite her telling you to stop and not replying could become problematic