A Johns Island woman faces up to 20 years in prison after she allegedly stole a $270,000 diamond ring while attending a party at a ritzy home along Connecticut’s Gold Coast.

Police said 21-year-old Juliet Jayne Branch was attending a birthday celebration at her boyfriend’s Greenwich home in October when she helped herself to a 10-carat ring that her beau’s mother left on a counter.

Branch told investigators that the ring somehow ended up in her purse after she got drunk and decided to try it on. She later sold the hand-crafted piece in Atlanta for $20,000, according to an arrest warrant.

Branch now faces a felony charge of first-degree larceny, which carries a penalty of one to 20 years behind bars, authorities said.

The ring belonged to Alease Fisher, a high-end fashion designer who was hosting a party for her son Andrew at their historic manor home, known as Chelmsford.

Not feeling well, Fisher went to bed early that night and left her wedding ring in the kitchen. When she returned the next morning it was gone, police said.

Fisher didn’t approach Greenwich police until February, when she found some incriminating evidence on her home computer. Branch, who by then had moved into the home, had left her email account open on the screen. Fisher scanned the emails and found messages Branch had sent to a friend in Charleston with attached photos of the missing diamond, police said.

Fisher told investigators she first became suspicious when Branch returned from a Thanksgiving trip to South Carolina flush with $15,000 that was supposedly a gift from her grandmother.

That struck Fisher as odd, as she thought Branch had claimed her family was poor, police said.

When detectives confronted Branch in February, she initially told them she knew of the missing ring but had never seen it in person. Her story changed when investigators showed her the emailed photos of the diamond, police said.

Branch told police she wasn’t sure that the ring was even real when she first tried it on. After she determined that the ring was indeed authentic, she decided to unload it during a November trip to Atlanta to visit her sister, Ashleigh, according to an arrest warrant.

Branch’s sister helped arrange its sale to a Georgia jeweler and took a cut of the $20,000 sale price, police said. She didn’t know the ring was stolen and has not been charged in the case, according to police documents.

Investigators tracked down the jeweler, but he told them in February the ring was missing again. He told investigators it was in a gem pouch that had been stolen from his truck, but there was a chance he could get it back, police said.

Greenwich Police Lt. Kraig Gray said the ring still has not been recovered.

Police arrested Juliet Branch on April 19. She was arraigned in a Connecticut courthouse on May 3 and remains free on $1,000 bail, authorities said.

No one answered the door at her family’s home Tuesday in the Stono Pointe subdivision. Branch’s attorney, Michael Jones, would not say where she is. He declined to comment on the charges, saying he is still reviewing the police documents.

Fisher also declined to comment on the incident, which she called an "unfortunate occurrence." A police document states that her insurance company paid her $223,467 to cover the loss of the ring.