Thanks for sharing your story.

I also disagree with Yury that hydration is over-rated. He may be the only person I've ever heard make that comment. It's essential to hydrate, and most beginners will never drink too much. I've been hiking for many years, and don't know anyone, nor do any of my hiking friends, of someone who overhydrated. Mostly it's a myth - drink more fluid than your body needs and you'll simply pee more often.

Taking 8-9 hours to reach the switchbacks is a tad slow, but not alarmingly so, all things being equal. On any given summer day, my hunch is lots of dayhikers are in the same boat.

One last observation - another alternative in your situation was for your companion to stop on the trail and wait for your return, assuming she still had adequate food and water. That would have given her 2-3 hours to rest/recover, although one wonders whether she would have actually waited, given her performance to date.

Hope you have a speedy recovery.