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
Girls 4-8 Barbie Dorm Nightgown & Doll Nightgown
BARBIE Nightgown Girls (4/5) Matching Doll Nightshirt "YOU CAN BE ANYTHING" $36 | eBay
Mia Belle Girls Barbie Inspired Nightgown | Little Girls Pajamas