Seconding everything AMDressage says (yes, FEI classes cannot be called).
If your friend is at all nervous, by all means she should have her test called. Personally, it may be wimpy, but I have had my classes called at every level through fourth. Not always, but if I need it, I ask. In part, if I’m riding a bunch of tests, I don’t want to have to worry about forgetting part of a test. I can never remember where one or two rein release circles fit in. In part, I know I can get lost in the test and I don’t want to have to worry about that. In LARGE part, I’ve found that the voice of a friend/trainer in the background of my mind can make me feel more settled, even if I totally know my test. There’s no penalty for it whether you are an amateur or professional trainer.
At one local schooling show, I’ve been one of their “professional test callers” because the organizers wanted to take the pressure off of participants if they wanted it.
Nothing wrong with a test caller if it will help the rider!
J.