How to remove a Gmail from the App Store

Your Mom may have signed into Media & Purchases with her account.

In the support article: If you subscribe to Apple One and use a different Apple Account for iCloud - Apple Support Apple alludes to using a different Apple Account just for media, subscriptions, and purchases, but doesn't describe how to do this. See if these work:

In iOS/iPadOS: Go to Settings > [your Apple Account at the top] > Media & Purchases. Sign out of the current ID and sign in with a different one.

On a computer with Ventura or later: First, quit Settings. Then, in App Store, choose “Sign Out” in the Store menu, then click on the “sign in” button that appears in the main window. You can then sign into the other account. (from: Using different Apple ID for media & purc… - Apple Community )

Related to that is: Use a different Apple ID to share purchases with Family Sharing as outlined in Use a different Apple Account to share purchases with Family Sharing - Apple Support

Also note what it says in this article Make sure that each family member has their own Apple Account - Apple Support

- "If you want to share purchases or subscriptions with family, use Family Sharing. Each person should use their own Apple Account.”

Note that if she downloaded any app with her account, the device will need to be signed into that account in order to update it. It is not a good idea to let anybody else use your iPhone and certainly not to let them sign into it anywhere.

Are you using your own Apple account? Or are you using your Mom's The App Store will reflect whichever email address is listed in the account.