She's not a big actor at all, but she was in the movie Jason X, and this scene in particular stood out. Jump to 0:40 secs and 0:43 seconds. Both happen pretty fast. It's probably worth getting a digital copy and playing it at 1/4 speed.
https://www.youtube.com/watch?v=m-5pPy7zuyc
the part where she's sitting in the background too:
28:55 of the full movie has a really nice shot of her spine. I can't screenshot due to youtube.
1:24:11 has a really nice shot of Lexa Doig's spine