Your mom paid the fine how? With a check? How much was the fine? She didn't notice that the check didn't clear?
We would have no way of telling you why you didn't receive a letter to your personal Post Office Box. You'll have to investigate that yourself.
Is mom going to come with you to court to indicate that she paid?
Having all fines paid and your license reinstated by the time you go to court could be helpful.
I can't promise you what plea offers the prosecutor will make, or whether you would get a better offer if you have a lawyer. You can consult a lawyer to see if it might be possible to work out a deal in advance and possibly to avoid going to court; it may be, but again that's nothing we can promise.

