How long have you had the lights? Quite often turning them off for a couple of days and letting them fully charge back up again in the sun can get them working, or if they are the type that has a battery, you can change I'll do that. It doesn't always work though, and they'd have to be replaced. You do have to use rechargeable batteries for them.
You're not actually learning Spanish with her then, how do you know if she gets it right if you don't understand her?