Contacts Syncing From My Sisters Phone

I upgraded my iphone 7 to an iphone 11 and gave the 7 to my little sister, she finally got a sim card in it recently but now her contacts are syncing onto my phone (ex. my moms contact is no longer the picture and the name i choose & her friends phone numbers are being added to my contacts) i already checked both our apple ids/icloud’s and they’re not the same, i cleared my data from her phone when i transferred it to mine, she isn’t getting any of my contacts, i just wanna know how to stop it.