alt Hacker News> moving my legs using her upper body, it felt quite intimate and I admired her for being so professional
This highlights something that I've been chewing on a lot lately. I'm not sure what you specifically meant by the word "intimate" when you said that, but I do think it's really interesting to distinguish between "intimate" and "sexual", even though they often coincide.
As an example, years ago I was staying with some out-of-town friends after a break-up and they wanted to introduce me to a couple of lovely single women they knew. I hadn't really been taking great care of myself in the fallout of the breakup, so I went and shaved and got cleaned up. While doing my hair, I realized that my eyebrows were pretty unruly and somewhat sheepishly asked my friend's wife if she'd be comfortable taking some tweezers to them and helping me get them cleaned up. It wasn't, even a little bit, a sexual moment but it ended up being incredibly and unexpectedly intimate. We were both pretty surprised by it and ended up getting closer (as friends) afterwards.
What a nice story! Cleaning up eyebrows shows nicely the discrepancy between intimacy (feeling love and care) and erotica (feeling lust?).
The hair grooming in the article probably felt similar.
Thinking about the physio therapy, her upper body felt very warm and soft but it was probably a rather standard technique for firmly moving the joints and ligaments in legs and hips.
What it made most intimate was not just the softness of her body but also the care she took for the movements, knowing that it would help.
So my limbic system went into oxytocin producing mode, which the aware mind easily picks up with warm thoughts. I think that's where the bridge between intimacy and sexual thoughts can happen, but there my thinking was not firmly going into that direction, it just felt warm and comfortable, even a bit emotional.
In your case the feelings apperently came from both directions, it was not a professional/client context after all.