Young and dumb and totally clueless.

So, I have a new co-worker. She makes the 8th in that position in 3 years. She's 22 and as dumb as a box of rocks. We work in the medical field, supposedly shes been doing our job since 16 years old, which I know is a lie because you have to be 18. She doesnt know how to use medical equipment the right way and it's annoying. She doesnt listen to me when I instruct her on the policies, I warned her and told her not to barge in on an ongoing appointment because the provider would be mad. Her reply? "I dont give a f@ck!" and she walked in and interrupted anyway for something that wasn't an emergency. She was told by me that she had to assist in a position and who she would be going with to which she replied "I dont give a f@ck who she is, main coworker in that position, Im going with who I want". I had to yet again, tell her that's not how it works and she is to go with who shes told to go with. She keeps wanting to use my sign in to do the charting even though she has her own. I keep telling her to talk to the boss to get it all straightened out. I dont allow her to do it under me. I think she is Narcoleptic because she falls asleep at the drop of a hat. She's done it in front of 5 higher ups as well as our boss, among multiple others in our department...and she snores. She claims it's her "allergies" and shes "congested". I have major allergies. I know the signs and she has none. She was called out by a higher up, whos new himself so I dont think he would report her just yet, and then thanked me, sarcastically, for not having her back. Im not getting into trouble for her. 2 others have been fired for their own wrong doings but because one used to be my specific co-worker, Im blamed. I want nothing to do with her and her wrong doings. Im just there to do my job and go home. I dont know how to deal with her annoying behavior and Im not a tattle tale. She also has a 2 year old who she blames EVERYTHING on and constantly says shes trying to get him into commercials so he can pay his own way!!! Hes on the spectrum. I feel so bad for the kid. She's way to immature for this position. I cant even get to the restroom without her following me, thankfully it's a single person restroom. Im on vacation for the next 3 weeks and am hoping she won't be there when I return, but if she is, how do I deal with the fact that shes to immature and doesn't listen? Ive had higher ups ask me if I think she will make it, to which I reply "no" and they agree. She is also trying to get personal information from me to tell my other co-worker/ex-friend, who is another whole can of worms, so I dont say much and if I do, it's what the other already knows, but you know how you can tell when someone is fishing for information. Im at a total loss and mainly just needed to vent, but any advise would be greatly appreciated!