Is there such a thing as text messaging etiquette?

[SYSV1RUS]

I know this female friend. She seems to like me just fine. She will ask me to meet up with her etc. I have no reason to believe I'm a blow off. Now for the confusing part. She almost never initiates a text message. I always send one first. That part I don't care about so much. The part that kind of confuses me, is at times she will either ignore my message or she will take a day to reply. Even that is no big deal. She could be busy, maybe she doesn't know what to say or maybe she forgets to respond. Now for the part that really gets me. We can be exchanging text messages and all of a sudden she just disappears. I'll sit there and wait for a response only to realize after a few minutes, she left someplace. I can understand this happening once in a while but isn't it considered proper to say goodbye if you're walking away from a currently running textersation? I guess everyone is different, so I should just accept this as part of her unique weirdness.Should I say somethg?