Last Summer in the Hamptons (1995)
Film directed by Henry Jaglom and starring Victoria Foyt and Viveca Lindfors.
Filmed entirely on location in East Hampton, Long Island, "Last Summer in the Hamptons" concerns a large theatrical family spending the last weekend of their summer together at the decades-old family retreat which economic circumstances have forced them to put on the market. Victoria Foyt plays a young Hollywood actress whose visit wreaks havoc on the stellar group of family and friends - led by matriarch Viveca Lindfors and made up of an extraordinary mix of prominent New York actors, directors, and playwrights. In the course of a very unusual weekend, comic as well as serious situations arise, and the family's secrets - of which there are many - begin to unravel. (written by Rainbow)
Raïna Paris plays one of the theatre audience.
You can watch the full film here.
Very special thanks to @74paris for sending me the link to the trailer of this film.