Has anyone ever obtained guardianship of an elderly parent with dementia?

You have a valid POA? You got this while she was still competent? If so, depending on the wording of the POA it may not be necessary to get guardianship. I went through a very simple uncontested guardianship process. It took about 4 months and was about $4k.

I did the same 2 years ago. Mine took many months to get done. Part of the process includes a court visitor to both you and your mom to evaluate her need for a guardian. Dad contested which made it cost more. We finally settled without a court trial and did a 'stipulated judgment'. He wanted it stipulated that I could not sell his house, his cars, nor move him to assisted living unless a physican said he needed to (that was easy when the time came). But when they say that guardianship gives you more control, yes it does but no it doesn't with a stubborn senior. He would not move out of his house until he had to go to the hospital and the doctors said he could not go home. Just be prepared: guardianship is a LOT of work. I do well with the bookkeeping part (if you are going to be is conservator) and you need to file an annual report, but dad greatly resents the amount of control I have. He does not cooperate with me and hangs up the phone on me constantly, I've had to learn to let a lot of stuff go. My siblings do not endure the same. You need to be prepared to be on call pretty much 24/7. You will be the first contact for anything he needs. This has been a lot of work and a lot of responsibility. I have often questioned my decision to take this on.

Yes it's better to have a lawyer, and yes the process could be expensive. It depends on what you want it for. If your mom refuses to go to an assisted living facility or nursing home, but she seriously needs that type of care, a guardianship is an option. Have you done a Healthcare Power of Attorney? I think those are only effective when the grantor is incapacitated and unable to make health decisions for themselves, but I don't think it stretches as far as placing someone in a care facility if they refuse. Not completely sure on that one. A good lawyer should give you a 1 hour free consultation, so I would at least do that and look into both, and other suggestions they might have. Best.

I did. The time it takes and the cost depends on whether your mother objects or consents to your petition. If she objects and you go to trial then that is big $$$ and many months of evidence gathering and proving incompetence. If she consents, then it still isn’t cheap but the time frame isn’t long. 4-6 weeks
in my case. It isn’t something you do without a compelling reason ie. she is a danger to herself and is resistant to care and won’t cooperate with you because of her incompetence.