Hello, Welcome to ComputerHope.
Due to forum regulations, I bleeped out your full email address.
Anyway, I am afraid we cannot help you in any way... Primarily because we can't do anything.
If there is no way to prove to Yahoo that your account was stolen, there is absolutely nothing you can do. Sorry.
What you
could do is create a filter on your mother's email account to automatically delete all incoming emails from
[email protected].