No. Not legally, and not at all on a phone that has been hacked or jailbroken. The only way to do it without hacking the phone would be if you have find my iPhone enabled and someone has your Apple ID and password. you can avoid that by changing the password on a regular basis and keeping it fairly complex.
Alphajets did you find out if someone was in fact following your mom? Kilted Tim's answer was what made me aware that the troubles I was having with my iphone5 was due to a boyfriend having some idea on my apple ID's password. Of course he will never admit it. So I'm not even gonna ask. I got a whole new apple ID that's hard to remember and set a password no one will ever figure out or find written down anywhere. That's what your mom should do. All good things can be turned around and be bad things too....this is just one classic example