Tell her you’ll fix it if she gives you power of attorney.

No, I’m not joking.

If you are having to spend 8 hours to figure out how to help her manage her basic affairs, if you are constantly teaching her how to use a password manager and she cannot figure it out, she has diminished cognitive capacity.

If she has already delegated you to be in charge of all her account logins, she’s basically already given you de facto control over them, already acknowledged she isn’t capable of of managing her own affairs.

Gather a bunch of other evidence that she has trouble with basic tasks, can’t reliably perform basic household activities, manage finances, whatever, approach a lawyer and get the power of attorney document(s) drawn up.

EDIT: // Holy shit, just saw your other comment:

Well I also cook everything, grocery shop and fix everything (basic electrical, plumbing, woodworking, installations, etc).

Yeah, you are already functionally her caretaker.

Depending on the state you’re in (assuming you are in the US) you might be able to actually get yourself certified as her caretaker without much or any actual input from her, before you pursue power of attorney. //

This solves the cut out problem.

…

After that, explain your solution:

Print out a big list of all those passwords and logins for her.

Meanwhile, you’ve got them all as well, presumably you can just use her password manager and have access to it.

If she resets a password and can’t figure out how to log back in, fix it back to something you know, but don’t let her use this account for one week.

After a week, print out a new list for her with the new password you’ve set.

If she resets another password while in a 7 day timeout period, well now it’ll be two weeks for both passwords to become available to her, etc.

This may sound like too much, but she’s a cognitively diminished entitled brat, who has already conditioned you into being a doormat who is expected to waste a seemingly endless amount of time and effort to solve problems she creates, problems that people without a live-in technical support agent pay hundreds of dollars to solve.

She will not learn if she has no impetus to. She’s obviously used the ‘tough love’ model on you, use it back on her.

If she complains about this, doesn’t matter, you have power of attorney, send her to an old folks home, sell the house and move to an apartment, or rent a room out if it or something.