Whatsapp — my whatsapp contacts showing on other phone

My whatsapp contacts showed up on my mom's phone. Not some... All of them. I have a moto g5 and she has lenovo k6 power. We don't have any kind of account in common.. Gmail, facebook, truecaller anything, so please don't reply me with "try to delete a common account". I checked in her contacts app, when i selected whatsapp in 'contacts to display' all of my contacts along with her showed. When i selected ony her google contacts and sim contacts non of them showed. So i'm pretty sure it's whatsapp. So please help me. This is very bizzare... And problematic. Please reply me asap.