My brother-in-law is dressing my 60-year-old sister with dementia in inappropriate outfits. What can I do?

If he's doing the shopping could it be that he is just totally clueless about size and fashion and then is too embarrassed to return clothes and too cheap to to discard what he already has? (in other words a typical man lol)
If you brought some more suitable outfits would he be willing to put them on her? You won't need to break the bank if you are willing to shop at thrift stores.

Thanks for clarifying. Maybe he just wants to do what she asks of him. It is strange though. Maybe stress the danger of another fall due to the high heels.

My sister's own husband is dressing her, or letting her out, dressed in ridiculously revealing and inappropriate outfits. She has dementia and thinks she is a junior petite size, in her late teens (she is 60), and she chooses to dress like a junior high school kid. She has gone out in spaghetti-strap-micro-dresses (looks like a shirt) and three-inch platform shoes: nothing like tights or pants in addition to the micro-dress, just the super-short top.

Whose husband is dressing whose sister? Why does she need help getting dressed?

The leggings are more like pantyhose or tights than the modern thicker more covering leggings or jeggings.

She is 60 yo, grossly overweight and bloated from prednisone, and he takes her out in skin-tight leggings, and I mean skin tight, skin tight low-cut tops that cover nothing, and three-inch platform shoes. She wears dresses more appropriate to an eight-year-old; short, short dresses near the crease of the hips that look like she is wearing no pants under them, and daisy duke shorts with high platform sandals. She has fallen in the platforms once already. If she were aware, she'd be mortified. I have spoken to him and explained how revealing and unbecoming these things are on her, but he continues to buy these clothes for her.

Cathie, what do you mean inappropriate outfits? What might be inappropriate to one person may not be inappropriate to another. Need more information.