I had another lesson with her. Was a bit more fun/flirty/cheeky than in the past.
Also, and more importantly, I learned that there is another instructor that I can get my tailwheel endorsement with in the same airplane I currently train in.
This knowledge empowered me send my instructor a message and invite her to go to what some would consider a somewhat romantic event with me. She wanted to go, but had another (legitimate) commitment already.
Dude....
Never use a text message or email to ask a girl out. There's nothing less personal than a wall of text. You were in a flight with her. After landing, on taxi back to the hangar, that's when you say "Hey, what are you doing tonight - want to go do [insert some form of foreplay here]?"
Never, never, never ask a girl out via text message unless you are in high school and you're trying to avoid catching the teacher's ire for talking during class.
NEVER.
You can fix this - but you have to drop the damn text message idea and just ask her out next time you are together.
Edit: My suggestion to fix this: Next time you are flying, after you're done, tell her something like "So, I know I had to reject your last attempt to go out with me, but I have a personal policy to avoid accepting dates via text message...I mean, how lame is that? Anyway, I am available tonight, if you want to try to make it up to me for such a lame attempt at asking me out."
Then you've injected humor, some self-degradation in the face of a poor decision, and you'll actually have a shot at winning her over. The alternative is to just become Don Juan and as soon as the flight is over, grab her, kiss her, and hope she doesn't slap you.