My mother-in-law has advanced vascular dementia, and it’s very hard for me to get her up during the day to feed her lunch. She flatly refuses.

Older people will lose their appetites. My mom was never a big eater but she ate even less as she aged.

Have you tried bringing a tray to the bedroom for her to eat from her bed? Does she sit up by herself?

What about having her doctor order a hospital bed? Or better yet, start looking into hospice organizations.

Have you considered placing her in a facility so you can rest? You can oversee her care and be an advocate for her.

Does she drink more than she eats? My mom enjoyed smoothies that I made for her.

I hope you will find a viable solution soon. Wishing you and your family all the best.

If MIL qualifies financially and medically she could be in a nice LTC facility that is covered by Medicaid.

Get her doctor to order a hospice evaluation stat. In the meantime, leave your MIL alone to sleep as much as she wants. Hospice will bring her a hospital bed to facilitate easier brief changes, and if shes not eating or drinking much, her urine output will be minimal anyway. Hospice can catheterize her once they're on board. Advanced dementia of this magnitude means she just needs to be kept comfortable until she passes.

Best of luck to you.

Have you tried getting her a hospital bed with a side table so all you have to do is raise the head and push up the side table with her food on it so she can eat if and when she wants?
And if she is in end stage vascular dementia I would bring hospice on board as they will supply a hospital bed and any other needed equipment, supplies and medications all covered 100% under your MIL's Medicare. They will also have a nurse come once a week to start and aides to come bathe her at least twice a week.
And she probably can no longer get out of bed. My late husband who had vascular dementia was completely bedridden for the last 22 months of his life. I had to hire an aide to come put him on the bedside commode every morning to he could poop.
Along with getting hospice on board it may also be time to have your MIL placed in the appropriate facility. Hospice can help you with that as well.
And please know as well that when someone is getting ready to die they won't want food or drink, and it can cause them great pain if either is forced as they're digestive system is the first to shut down.

Why would you do this? The truth is that as we age almost NONE of us eat three or even two meals a day. I certainly don't at 80. I eat when I want and what I want and there's no set rhyme or reason. What possible reason to force this person, with so many loses and so few choices to get up and eat. We sleep more until we get the big sleep. She is on her way to dying, not on her way to turning life around and a return to childhood. Please allow her some peace and honor her wishes.

How old is she? Does she have any other health issues? The answer may be that she may now need hospice care if she's refusing to eat.