Thank you.

My guess would be it was 95% driver error (and hopefully she didn't do too much damage, since it will be deemed entirely her fault) because I've never hydroplaned nor slid while braking on this car. I've done almost full out panic stops in downpours and have never slid an inch. That's what the ABS is for. I would say it's rather clear that she misjudged her distance and didn't brake correctly, as ABS is rather loud and obtrusive in the 6th gen Accord.

The only really possible cause of brake failure would be inadequate brake fluid or stuck pistons. On a MY2000, I doubt it has a stuck piston. My right front piston sticks from time to time (I need to get a caliper rebuild kit) but my car is still able to brake very quickly. To have all 4 pistons stuck? I'd say the odds of that are pretty astronomical.

If the ABS light was not on at the time of the accident, your ABS was working. FYI, if it came on only after ABS was activated, the ABS system worked for the panic stop and then shut itself off because of an intermittent failure.

The only real way to skid in a modern car with ABS and good tires is on ice or snow. Brake failure is highly unlikely - I would imagine she wasn't paying attention and only braked at the last second, or misjudged it completely.