Amandine Hesse is a pretty classy player WHEN on form - she's one of the most mercurial players on the circuit. With a lot heavier ball than Katie's.
So, without having seen it, I don't think Katie necessarily had an off-day or that it was very surprising she lost heavily - she was playing a player who is a fair bit better than her (at the moment) and a LOT better than her (at the moment) when she's on song.
I never had Ms Hesse pegged as a future top 100 player, so for me, I don't know about anyone else, felt Katie had a real shout here of an upset. I am a huge believer in not only Katie's future potential, but also her current potential. I certainly saw that 1st hand in Eilat, and even in her performance at Sunderland albeit she wasn't at her best there. So to end up at the scoreline we had today with only 80 points played, I would say its a combination of 3 factors assuming of course Katie was feeling 100% : 1. The matchup/Hesses's style of play just didn't suit Katie 2. Hesse played a 9/10 match and 3. Katie did have an off day. So that's my speculative answer.
Amandine is a complete headcase - about the worst I know. But she's 160 or so in the world, and going up. I believe she'll make the top 100. In training, she's always been about the same as Kiki Mm they've been playing together since kids, with no real difference between them. (Apart from the fact Hesse only needs a buzzy fly to lose it completely, or trips over a daisy, or ... or ...).
I haven't seen Katie since last year (when I saw two of her matches) and completely agree about her potential, and her 'current' ability (which, presumably, has got even better since last year). But I think Amandine playing 9/10 still beats Katie playing 9/10 very easily. However, as you say, it's pure speculation. Katie tweeted a chirpy, upbeat tweet so she'll put it behind her, as she should.
A huge well done to Gabi - an excellent tournament following a 'slight' disappointment last week - Harmony Tan lost easily to Zarazua in R1 here (after having beaten Gabi last week in a match many thought Gabi stood a good chance of winning)
A huge slice of luck, which you can but humbly accept.
Would be nice to root out some details about what the injury was, and exactly when it occurred.
$25K SF is a good level to experience however you get there, and Gabi had to get this far to have the opportunity to benefit from the good fortune anyway.