gallery sims reverting back to original version

i have a sim that i met off of cupids corner, they were really compatible with my sim so when i moved them in i changed their appearance. every time i leave the lot she changed back to her original state completely. it wont fix itself unless i go to “change sim” in the mirror and it will be the way i edited her again. every time they travel anywhere this happens and has been happening for months. i play on xbox with no mods and i’m also not using cheats on this save.