Elder Granny - no nsfw - always in lingerie

replace sleep outfit with something other than lingerie? assuming she is in sleep outfit

or if its orange base outfit bra and panties then yeah you might have lost whichever thing she was wearing and have to give her new outfit in cas

you also might have multiple outfits in same category for sim so maybe one of the extra outfits lost and thats where they have bra and panties

or yeah it could be some mod thing

As others have said you are free to change outfits via dresser and (I think) mirror.

If this is a sim from the Gallery wearing clothing from packs/kits you don't own the game is supposed to replace it with clothing you do own but sometimes it's removed altogether.

So funny. My Ulrike Faust is now a granny still sporting her sexy sleepwear half the day. Can change easily enough but keep forgetting.

Has she been wearing any cc that you have removed from the game?