This- your insecurity over how quickly she responds had nothing to do with her level of interest aside from the fact that most people will get tired of being held accountable to the thoughts in your head.  

Meanwhile, case in point, my soon to be ex will text me all day long about insignificant shit but once I'm home in front of her she won't say a word and has no interest on me at all.  So yeah, it didn't mean a thing other than she didn't have anything to say that was important enough to drop what she was doing to put together a response.