Did you even read Sniper's response? Especially this part:
The officer can write the citation as an "owner responsibility" ticket but at any rate, and regardless of whether you thin it is fair or not, the law states:
4000. (a) (1) No person shall drive, move, or leave standing upon a highway, or in an offstreet public parking facility, any motor vehicle, trailer, semitrailer, pole or pipe dolly, or logging dolly, unless it is registered and the appropriate fees have been paid under this code or registered under the permanent trailer identification program, except that an off-highway motor vehicle which displays an identification plate or device issued by the department pursuant to Section 38010 may be driven, moved, or left standing in an offstreet public parking facility without being registered or paying registration fees.
Even if the officer were to have written this as an "owner responsibility" ticket, the mom would still have to pay the registration fees and get the correction within the same time period that she would have done so when the ticket was written for her daughter. So nothing changes there.
Add the fact that your niece simply choose to ignore the whole thing until the late fees were added, and the problem got compounded accordingly.