What is her endurance/strength? Pregnancy, Inflation, or oversized breasts can cause slaves to crawl depending on their strength/endurance to carry the extra weight.
Also, have you ever used handcuffs on her? There is a glitch with that atm
Her strength is at 7 and endurance at 4 so I doubt it's that. She isn't pregnant or anything either. I have used handcuffs on her though, might be it, is there a way to fix it ?
For now, the most straightforward method is editing the save file (using something like notepad+) and looking up “restrained”: “cuffed” and replacing with “restrained”: “none”