essentially anything, as long as it isn't for being part of a protected class.

If she signs an employment contract then she needs to be concerned about resigning w/o satisfying it, but it doesn't sound like she has. Best for her to refuse to sign and let the chips fall where they may. Sounds like he values her as an employee if he's willing to pay 13K for a CE class for her and therefore she may very well keep her job even while insisting on remaining non-contracted.