Stree is a ghost with powers in braid.
The plot is based on the Indian folk legend about a female spirit who attacks men at night if they are alone and only leaves their clothes behind. The residents of a town named Chanderi, Bhopal believe in the spirit of an angry woman, referred to as "Stree", who stalks men and whisks them away during the four days of a festival every year, causing many disappearances.
For the question:
There are also references to her ponytail being the source of her powers indicating that she is a witch of sorts.
Some noun meanings of witch:
1) a woman thought to have magic powers, especially evil ones, popularly depicted as wearing a black cloak and pointed hat and flying on a broomstick.
2) an ugly or unpleasant woman.
synonyms: hag, crone, harpy, harridan, termagant, she-devil;
So, we can say that Stree is a ghost with powers in braid.