If she has bad reception in her area, it can take hours to receive messages. I know it's hard to not over analyze everything, cuz I do it too but try not to, it will drive you crazy. Don't constantly send her texts asking why she doesn't text you, I don't see it as stalker ish but it might annoy her after awhile.

Try not to over analyze things too much. She seems to like you as a friend at least and may not want to text back immediately as may have other priorities.

Let her get to know you gradually without being too pushy. I know from experience that the dreaded "did you get my last text?" / "why aren't you replying?" never goes down well and just makes things get heavy. If she's genuinely got a problem with her phone and wants to stay in touch, let her text you. Maybe set a rule never to text her unless you've had one from her first. That way you can't possibly some across as stalkerish or too desperate.

I know from experience that too much obsessing over relationships or friendships can make a good situation turn bad. Just keep it fun and light if you can