You might need to ask those questions in a general health forum; I've sure there's probably one on here. Or something about hypochrondria? I have had anorexia many years and never faced any issue like that. It might be some type of OCD or paranoia?

I don't know your living situation exactly, but if anorexia plays a role, it could be ED-thinking does not want an extra set of eyes around watching you & your ED behaviors (I had some weird ones, like hoarding food under my bed and such), and hence you come up with all these very unlikely scenarios as to why you should not accept this new roommate? But it's all just a guess.

Truly, though, I doubt the person has a horrid, incurable disease. Furthermore, if you're worried about TB, there is the vaccine against it. Though they do a skin test first first that needs to be read 48-72 hr. after given. There can be false positives depending on the circumstances, but if the doctor is worried, there is a vaccine against TB. The vaccine is thought to last 15-20 years, possibly longer. So if it's been awhile since your last TB test, get another test & a doctor's opinion as to if you need a vaccine, and don't worry about it.