iOS app keeps showing previous account after sign-out, reinstall, and signing in with a different account

I accidentally signed in to my own NextDNS account in the NextDNS iOS app while setting up my wife's iPhone. Since then, the app always shows my account and profile on her phone. Signing out and signing in with her account from the in-app settings and profile menus does not change it. Deleting and reinstalling the app does not clear it either.

This looks different from the shared-keychain behavior described in "Profiles Being Overwritten and All Syncing to Single Profile" (https://help.nextdns.io/t/q6ygfmx). My wife and I use separate Apple IDs, so our iCloud Keychains are not shared.

Environment
    •    Device: iPhone 15
    •    iOS version: 26.6.2
    •    NextDNS app version: 3.2.1
    •    Apple ID: her own, separate from mine
    •    iCloud Keychain on her phone: off
    •    Two separate NextDNS accounts (mine and hers)
Steps taken
    1.    Deleted the NextDNS app.
    2.    Confirmed no NextDNS configuration profile was installed (Settings > General > VPN & Device Management).
3. Cleared website data for nextdns.io in Safari.
    4.    Checked the Passwords app. No saved NextDNS credentials.
    5.    Restarted the phone.
6. Signed in to her account at my.nextdns.io in Safari and followed the iOS setup link to install the app from the App Store.
    7.    Opened the app. Before any sign-in, it showed my profile at the bottom of the screen.
    8.    Signed out and signed in with her account from the in-app settings and profile menus. It still showed my profile.

Repeated steps 1 through 8 several times with the same result.

Expected
After reinstalling, the app should start with no account, or sign in to her account when her credentials are entered.

Actual
The app restores my account on every launch, even after signing in as her.

Current workaround
I installed an Apple configuration profile from apple.nextdns.io with her configuration ID and selected it under Settings > General > VPN & Device Management > DNS. test.nextdns.io confirms her phone is using her profile. The app is still unusable for her account.

Questions
    1.    Where does the app store the signed-in account, and is it kept in the keychain after the app is deleted?
    2.    Is there a supported way to fully clear the app's stored account on a device?