I agree with this. It happens when over-processed. This happened to me at a salon several years ago. The ends were snapping off like rubber bands. Horrible colorist.I agree you should cut a couple of inches off.It really sounds more like something chemical going on than a heat related cause to me. My colorist mentioned once that is what happens when overprocessing occurs....the hair gets all gooey and elastic/stretchy like that...much like a melting effect. Does she just touch up the roots or highlight all over every time? You might have to get a few inches taken off to get rid of the damage. And I would go to another colorist for a consultation and see what they think may have happened. Good luck....
Condition like crazy, leave some K-Pak on your head overnight. The shampoo & deep conditioner are good.