My female black and white has always been very mellow and sweet. She is coming up on two years old now. The other day I had her out while I was preparing her food and I went to pick her up and she latched onto my thumb. She claimed down and did not want to let go. She bit right through my nail, and kept biting down harder till I finally got her off. I fed her and put her in her enclosure for the night, but she still seemed restless jumping at the walls of the enclosure. She hasn't acted like this before and I'm concerned about her and wondering why the change of attitude. Any help would be appreciated!