How to remove my number from another iPhone?

I checked my mother's phone today, and in the settings for messages, I saw she could receive messages that were being sent to my number. There were a list of numbers and E-Mails that she could be contacted by, and my number was on that list, on her phone. How do I disable this so that she doesn't go snooping around my messages?

Added (1). It was definitely an option for her to receive and send messages using my number.

Are you sure it doesn't just mean she can receive messages FROM your number? I've never heard of intercepting other people's messages. That would be illegal invasion of privacy.

Maybe these are "parental controls" if which case you don't.