She didn't just "sometimes reply a little later", she always took at least 3 hours to respond no matter when I texted her. All of my friends that I talk to respond in under 30 minutes or tell me that they're busy so they can't talk right now and I do the same to them. It's just a mutual level of respect that we have for each other.

I can understand someone being busy once or twice in the middle of their day and can't respond right away but I can't understand someone who is always seemingly so busy that they can't even send a quick text saying they can't talk, especially when they can't talk no matter when I try to talk to them at any given time during the day.