noun
1.
a long garment having long sleeves and tied at the waist by a girdle, worn under a coat in the Middle East.
2.
a long, full, usually collarless robe with wide sleeves that is worn at home for lounging or entertaining or at the beach as a cover-up.
http://www.dictionary.com/browse/caftan
What she is wearing has no sleeves. It’s a muumuu.