Re: how loud is an HT from the cager's perspective?
All of the info on legality for your state should be able to be found via googling your DMV and Mopeds in the same search.. That's how I found the laws for my state, and our legislature is so horrendous that they actually tried to abolish our state constitution and start from scratch this past election and rewrite EVERYTHING. So I can't imagine it'll be that difficult for ya.
Find the law as it stands. Talk to your local officers on the subject and they might be able to give you answers. I know that people here register their bikes using the date stamped on the motor and the engine type as their VIN..
from my experience the fuzz don't mind loud bikes, as loud bikes save lives. it's provoking or instigating situations that'll get their attention in a bad way.
Find the laws, show them to your mom. Let her friend look like a jackhole for thinking she knows anything about a subject she has no involvement in.