As much as we like to think that all our friends are great and trust worthy, it's never a good idea to give anyone access to your account (except maybe your mother).
I'm not saying that there are friends that you can't trust, there are, good one's are out there. I believe they are hard to find, but a good rule is don't let anyone else in your account to do something for you unless you are right there with them (but I still say play your own games, more fun that way).
As far as your account you can try to mail Neopets and let them know that you were not the one on your account at the time. I've heard of some people getting their accounts back that way. Just learn from this life lesson, and try not to repeat it, that's about all anyone can do.