Well, personally...I would ignore them...but then again, I'm not a nice person.
Well, it's more like I wouldn't know how to respond, and I'm a very "ignore the problem and it will go away" type of person.
But you could write her in English, and suggest that if she doesn't speak English to use babelfish or something to at least get the general gist of your message. Or you can use babelfish yourself. It's poop for a good translation, but it might give her the idea...
I took four years of French, but I didn't retain much. Merci beaucoup pour tout les cadeaux, mais n'utilisez tout tes Neopints pour moi, s'il vous plait!
That's the best I can do. XD Literally that says "Thank you very much for all the gifts, but don't use all your Neopoints for me, please!" Luckily it could all be said in the present tense because that's really all I remember!