Well if the people are any good even deleting the files wont do any good.
Here is a quick explination. When you delete a file it isnt really deleted. It is just hidden from the OS till something else overwrites it on the Hard Drive. That is why even after a format some things can be recovered.
So if your mom does get someone to look at this stuff then you could be in trouble if they are any good. They might just use a file recovery application and recover the files on the hard drive.
You might be able to use a application like Eraser
which does multiple sweeps over the files area. But even that isnt for sure.