In the last several months, my mother doesn't like to put on pants. She wears underwear, but doesn't like putting on long pants. She has difficulty remembering where her clothes are. When she finds some pants, or is presented with some, she often finds excuses not to wear them.
Is this a behavioral problem, or a sensory/health problem?
I know as I have aged, I had to change my dressing routine. No more standing up to put on slacks, needed a third arm to do that as one arm is on the wall to keep me from falling over, and pulling up slacks with the other arm wasn't easy :P
Now I sit on the bed to do the slacks. And learned not to wear fuzzy socks when doing slacks, otherwise those fuzzy socks will make it difficult to pull up the slacks or to take off the slacks.
Oh getting older is soooo much fun :]
www.amazon.com/Cotton-House-Dresses-Short-Sleeve/dp/B017HNESIM
Just a sample
Maybe the pants are too hard to put on? Maybe too challenging when she needs to use the bathroom? Would she wear a house dress? Or a robe that would also give her some kind of coverage?
Maybe you can observe her and ask some questions to try to figure out the source of her pantslessness (to coin a "word"). This could help you to "solve" the problem if you can understand the big why.