You did the right things checking her out as much as you can.
I guess I was just thinking if maybe she bid on, say, three items and she got neg. feedback for two very recently (all the same timeframe). And if she had perfect feedback previously.
Does that make sense? One time when I checked someone's feedback they had a lot of negatives at one particular time. The ebayer had been in a devastating car accident and was away for some time. When she came back her feedback from then on was all positive again.
Anyway, I am sorry she didn't pay you. That stinks.

I hope she comes through for you.
Best wishes.