Well I've read it (only you posts tbh as the other are advice rather than fact) and it seems to me that you have crossed some secret line that only she knows about.
I agree with 2P worth, it is very often the case that some people put out a lot of help chiefly to have their altruistic glory reflected by eternal grovelling gratitude. I am certain you haven't done anything purposefully or consciously wrong but she has had a secret criterion of thankfullness that you just haven't met overtly.
Don't worry about her anymore, you've paid back the money, addressed the issue and been adult, not much more you can do.
ah...passing on secrets
It's always a coutnerpoint between the exquisite thrill of telling and the agony of being found out.
There's no reason to think that just because you have fallen from her favour she's going to go blabbing, despite her idosyncracies she wouldn't stoop to that. (well that's been my experience and I'm a HUGE blabbermouth)