Whoops forgot to ask one more thing.
What is the significance of message length? How do I control this?
Also, is it smart to wait for her to iniate conversation?
Seriously, just calm down, and stop over-thinking things.
It doesn't matter if you send her a big text, or if you send her short little sentences.
If she's going to be insulted or stop talking to you because you sent a message that was too long or too short, then you don't want to be friends or anything more with someone as fickle as that.
Do you have other friends you chat to via text?
Like, people on Steam, or Skype, or friends via your phones?
If so, just talk to her in the same way you talk to them.