The teeth you're seeing aren't really like human teeth at all; as has already been mentioned, it a line of cartilage-like material that they use for gripping. The teeth aren't sharp; it won't hurt if they bite you. Think like rubber grips on, I don't know, the closest thing I can think of is an eyelash curler. When they "chew," it's basically them trying to get a better grip on their food while they slowly force it into their stomach.
In the video, it doesn't look like she's been eating, which indicates to me that she might be trying to throw something up. That could be sand. If there's sand around, they will likely injest at least some of it along with their food, which can cause problems (possible impaction, ammonia pockets in the sand, difficult cleaning, etc.), especially with young axolotls. This is why bare bottom aquariums are often used.
If she seems lethargic, that would seem to indicate some other possible problems. Have you done recent checks on water temp, ammonia, nitrites, and nitrate?
