Accessing accounts created with Hide My Email for a user in decline

My Mother-in-law set up accounts using hide my email and most of them she did not save the password. She is now in decline with Alzheimers and cannot communicate. We are trying to access these accounts and to find accounts that may have been set up. How do you go about this? We can find the email accounts that were created through her Apple ID and iCloud account, but have no idea how to enter them on the websites so we can reset passwords to get to information that we need. Plus, she was in decline at the time she learned to use them and we think that there are multiple accounts set up for one particular website, but we can't prove this because her hide my email info only lists a couple emails that were set up. Any help is greatly appreciated.