Long distance relationship problem a33

I'm (M19 ) and she's (F21 ) , Our long-distance relationship was actually going well, and we planned to meet next month. However, things have become a bit strange; she's been slow to reply, and we no longer talk in the mornings as deeply as usual. I've already mentioned this to her, and she agrees that it's only pushing us apart. She agreed with me, but the problem here is that this behavior continued from her (and from me spontaneously). I want to understand from your previous experience how you expect this to lead to what? And when will it really become a problem?