I think she was too CLOSE.
I think she "knew" someone, or something, that she hadn't "put together yet", and as such presented a threat to whoever "did" the anthrax.
Sooo, in that case, what do you do?? - You eliminate the threat.
It's the only scenario I can come up with considering no anthrax had been discovered "at" the hospital.
Just "how" you'd infect her, I don't know, unless you'd expose her to it in some way, and avoid it yourself OR maybe already be taking cipro and not be susceptible to it.
The thing is, I think she must have been too close to the source.
That's entirely possible. It's also possible that she just traveled or lived in the same general area as the terrorists and was randomly used as a test subject.