the one on SR-535, near Hotel Plaza Blvd (Downtown disney resorts) is the closest. If she has a car, it'd be about a 5 minute drive from Chatham. If she does not have a car, it's about a 20-25 minute walk, or you could take a CP bus to DTD and walk from there, probably about a 10 minute walk.
Directions (walking or Driving) from Chatham: Exit the chatham square complex onto a little 2 block long street that I don't know the name of, make the first left onto Little Lake Bryan drive (I think that's the name of it), follow that until it ends at Vineland, make a left on Vineland. Follow that until you reach 535 (Apopka-Vineland Rd), make a right onto 535. The clinic will be on the left hand side, after you pass under I-4, before you get to the Chilis.