Oh man, the bathroom photo betrayal is so real. I went through almost the exact same thing a few years back and it honestly changed how I tone check forever. My fix was pretty low tech, I keep a plain white towel and a mirror in my kit and I walk the client over to the window before I rinse, then snap a phone pic with the flash off and one with it on. Nine times out of ten the yellow only shows up in one of those two shots, and I'd rather see it in my own pic than in her selfie at 7am. I also learned to check the mids and ends separate from the root, because the root can look neutral while the ends are throwing gold. Station lights lie to you, they make everything read cooler and flatter than real life. Dana was a gift, she taught you more in one text than two years of staring at pretty swatches under bad bulbs.