How do I stop the smelly closet stench?

Take her to the doctor. They have remedies for this. Place baking powder in her shoes. Spritz inside of her shoes with rubbing alcohol. People also say baby powder. I would stay away from it as they have been slapped with lawsuits as it contains ingredients that cause cancer. Use plain old cornstarch instead.

It is nothing to be embarrassed about. Don't make her feel ashamed or uncomfortable. Everyone has some sort of issue. This can easily be remedied.

https://basmati.com/2017/02/14/6-home-remedies-deodorize-smelly-shoes

https://www.sweatblock.com/blog/remedies-stinky-shoes/

https://www.disabled-world.com/assistivedevices/household/tips/shoes.php

I use this method for closets, small rooms, and drawers. Helps with all types of odors: https://chemistrycachet.com/most-effective-way-to-eliminate-pet-odor/

Air fresheners in closet can help. Foot powder can help while wearing and after. Leave shoes out in garage to air out. Wash the washable shoes (canvas, sneakers).

Olds socks filled with kitty litter inserted into the shoes. Fabric sheets inserted into the shoes. Cedar hangers would help.

https://www.homedepot.com/p/CedarBerry-Hill-Aromatic-Cedar-Hanger-1-Pack-319/100134000?MERCH=REC-_-PIPHorizontal2_rr-_-100251133-_-100134000-_-N

Put baking soda in the worst shoes, like sneakers and boots while they are not being worn. Put an open box of baking soda in a corner of the closet somewhere where it won't get knocked over or on a shelf, it will help a lot, just like in the fridge. Leaving the closet door open will also help let fresh air into the closet. Hopefully her clothes don't smell like the shoe stench, Margie! I hope you find a satisfactory way to make it smell better. You can also purchase the air fresheners for absorbing some of it. I know my mom always put baking soda in our sneakers and it really helps.

Baking soda in shoes both when she wears them and when they are resting in closet;Activated charcoal use same way. Wash any shoes that can be washed regularly. Buy her leather or cloth breathable shoes/footwear instead of plastic feet cannot breathe in plastic sweat and odor occur also can cause foot fungus. Articles on plastic footwear https://www.vogue.com/article/the-dangers-of-plastic-shoes some more https://www.bergdpm.com/blog/post/should-i-wear-plastic-shoes.html

Don't wear the same shoes everyday. When taking off her shoes, leave them outside of the closet and open them up as much as possible. Then treat. Allow to dry thoroughly before using or putting them back in to the closet.