1) Stimulants are only prohibited "in competition," so by defintion, getting a TUE would allow her to use the drug during a competition (or, close enough to it to fail a drugs test).
2) Her TUE would specifiy the dose of the drug that she could legally use in competition. If she tried to go "off label" and take enough of the stimulant to affect her performance, the increased dosage would presumably show up in her test.