Forgot password to access Advanced Data Protection and other 'top tier' security settings

Hi, hoping to get some help for my wife - apologies if I don't get all the terminology right or don't know some details but she's extremely anxious about losing all her data and memories, so trying to help without pestering her with loads of questions!

Years ago (2010 ish), she set up what she calls the 'ultimate' or 'master' password for her Apple account, but has forgotten the password. I think this is what a number of the most secure settings are hidden behind for security. Perhaps 6 or 7 years ago, we went into an Apple Store to ask them how to reset / remove this ultimate / master password, and they said it wasn't possible. It mostly hasn't got in the way of day to day activities, and she's had new iPhones in that time as well (transferring everything across using iCloud), but as time has gone past, more and more settings / functionality are behind this password.

One of them now is the Advanced Data Protection, and as we're based in the UK she's really concerned that she can't turn it off (if it's turned on at all, she can't tell) she'll lose everything on her phone / iCloud account when it's fully withdrawn for existing users.

She has quite an old phone at the moment, I think iPhone 8 running iOS 15. She's just bought a new iPhone 16 to try and start afresh. She's set up a new AppleID and is slowly transferring everything over via Bluetooth, to keep things like the photo metadata so things appear in date order. Ideally she would be able to reset this password, or utilise another workaround to transfer data more quickly, before the ADP is withdrawn.

If anyone can help with this, or even just confirm the correct terms and things to use to help searching online, then that would be amazing!