The ex-girlfriend of late hedge fund honcho Donald Drapkin is waging a legal battle over the Park Avenue apartment she bought with him in 2013.

Elyse Slaine filed a lawsuit in Manhattan federal court claiming that Drapkin’s children are blocking her from taking over the three-bedroom duplex at 700 Park Ave., which she says the former Casablanca Capital chairman wanted to give her.

Slaine took over the $4.2 million pad after she and Drapkin split in co-op, Page Six reported at the time. Drapkin died last year in a skiing accident, prompting her to seek his stake in the place.

But Drapkin’s children, Matthew and Nicole Drapkin, who are handling their dad’s estate, have refused to play ball, the lawsuit says.

Matthew and Nicole Drapkin did not return requests for comment.