Why is Apple not sending password reset instructions for my mom's inactive iPhone?

My mom's iphone went inactive weeks ago as she probably attempted too many wrong passwords.

We're trying to recover her apple account as a first step while we don't have her password. Weeks ago, Apple's message hinted it will send that password resetting instructions to MY phone number (from the last 2 digits), after a few days, and I figured "great. So I must have had my phone number as a backup on her account". Nothing was sent that I'm aware of. So I attempted again and called customer service, who said it should eventually work. Now it says "4 days". We're patient, yet not so confident as I'm seeing other people post about this issue with no notification coming from Apple.

Please advise on why this is happening? I want to prepared just in case it fails again. Apple should make this a lot easier. Our phone bills are being paid while the phones are rendered useless with a lot of unknowns.

[Re-Titled by Moderator]