Briefs causing a rash-when dry

I myself cannot wear Always anything. I felt it was like plastic sticky to me. Switch brands. I liked Serenity from Walgreens.

Maybe switch to one of the washable incontinence underwear. they are more cloth, like regular underwear but with an absorbent panel that would probably be softer and less abrasive on her skin.
When she gets to the point of needing incontinence underwear you can either get a more absorbent one or add one of the pads to it either a disposable one or a washable one.

If she's only wearing the briefs "just in case" she may be able to switch to a pad, there are very large overnight ones that can hold a lot. Bonus is they will be less expensive and easier to change.

This is ordinarily a result of the plastic that covers the brief if you have tried several different kinds and any deoderant additives have been ruled out due to allergy to same. The plastic doesn't allow the skin to breath. There should be times when she sits on pass or incontinent brief, and times when she doesn't wear it.

Do know that the cortisone itself may be an irritant to skin, and my own produced a bad allergy when used in chest area for radiation treatments. I would switch to A&D ointment at night, and clean dry skin during the day, open to the air. If this continues, worsens, consult the doc.