If you check the first video for Trial Day 22 at around 1:26 you can see her do the same gesture. She has done this gesture at least 3 times, but I can't find the other example, which was prior to Day 22.
I think she is either communicating with someone, or she is attempting to get sympathy, as in, "Feel sorry for me because I'm done for." I find it highly unlikely that motion would be accidental or unintentional. It feels very unnatural if you do it to yourself and make contact with your skin, mainly due to a feeling of vulnerability around one's neck, sadly enough.