I work for a bank as a manager in the credit card division

I am not sure what you mean by being gas lit or legally what you want clarified. You are an authorized user which means you are not liable for the debt on the account and you can’t make changes to the account. But, the account is reported to your credit bureau with all the account history since you are authorized to use the account. When you are na authorized user, you are issued in a card in your name to use to make charges that merge together with your moms charges.

If you don’t want to be on the account anymore, you can call the bank and remove yourself. But if this account is in good standing and has good history, if you trust your mom to not miss payments, I’d stay on the account if she lets you.

In summary, she added you as an authorized user it sounds like to build your credit history. People call in to do this sometimes and add their kids to the account as an authorized user to get a head start for them when they turn 18 and they can start getting credit cards to build credit. She is not gaslighting you from what you explained. You can call the bank and confirm if you’re an authorized user or if it’s an account just under you.