iPhone 6s asking for iCloud login while turning on the phone

My mom's phone (iPhone 6s) is asking for iCloud login right after turning on the phone. Since she doesn't remember the password to the account, she's been unable to use the phone for the past week or so. I tried resetting the password in different ways. But in almost all cases, it asks me to check the email sent to her same iCloud email (with forgotten password).

With the other process, it asked us to wait for 4 days for account recovery. It said that it will send the password reset instructions to the linked phone number. It's been around a week now, and we haven't received it yet. When I try the same thing again, it's now saying 12 days of wait. And I'm not sure if we'll get it then.

Feeling helpless with the process. Help!

Fwiw: she is not in the US.