When cats shit outside the box, they’re trying to communicate something. Unfortunately they don’t speak English and sometimes resort to speaking Catshittese.
Are there enough boxes? You should have n+1 litter boxes, where n is the number of cats in the home. Also they should be scooped two or three times a day (before work, after work, and bedtime is a good routine). The litter should be about 3”/8cm deep: they need enough to bury their piss and shit, but too deep feels unsteady beneath their feet.
Is she a really big cat? She might want a bigger box. I once had a big fuckoff tabby who needed jumbo boxes with extra-high sides.
Maybe she’s having digestive pains. Does her shit look normal? If not, put the misplaced turd in a zipper baggy and have your vet check it out.
It could also be an emotional issue, like loneliness or anxiety or dominance, but make sure the litter boxes and digestive health are all in order before deciding that’s what’s up.