Alright, we are back from the exotic animal hospital. Thank you to all of you who gave me sound advice!

It turned out that the black stuff was merely coconut husk from her old owner's bedding, that she must have gotten in her mouth when eating or crawling around. There were several large chunks but the vet removed them easily and checked her over as well as sexing her. She had no mouthrot!!!! Yay!!!!!! (does happy dance)

She is indeed a "she", she is a Mojave as well (good find, eh?). I will post pictures once she has settled in and eaten for me at least once. He said that besides being on the skinny side, she is apparently healthy and looks free of parasites (at least external ones). She will be quarantined and hopefully will start feeding for me next week (at least I will try to feed her).

Thank you all again for the good advice! I feel much better now that she can close her mouth properly and is free from nasty splinters. This is why I have always used paper towels for my snakes.

Thanks again!