Perhaps it was because she and you knew someone mutual and she'd misled you about something and your relative could have busted her about it.
Having known you online for a while I believe you about your behavior. While of course our conversations have been limited to topics of Religion & Spirituality, and I'm an older married woman so you'd have never had a reason to flirt to begin with, you've always been a very polite person even before you knew those things about me.
I'll wager in this instance, it had to do with insecurity related to something about herself or fear that you may already know more about her than she wants known. Of course, not being present for both sides of any conversation, this is guesswork just based on being a Y/A contact of yours and reading your posts online.
edit: If you pay attention to the "logic" of Johan, you'll likely REMAIN single.