HMF this ballerina barbie nightgown that got donated. It came as a girl/Barbie doll matching set. This is obviously the doll one. Probably a girl size 6 from early 2000s : r/HelpMeFind
Barbie Doll Night Gown, Barbie Night Dress Pajamas, Barbie Pajamas, Barbie Clothes, Barbie Fashion, Barbie Pjs, Barbie Outfit - Etsy
Vintage 90s Barbie Nightgown Bride Flannel Night Gown Mattel Clothing Set Of 2 | eBay