The Liberties native and the soccer star have been spending the past few days in New York City as they enjoyed some Christmas shopping.
But she was left gobsmacked after her other half went down on bended knee and asked for her hand in marriage during their stay.
Delighted Sarah was quick to share their good news with their friends and family, posting a picture of the smitten couple online.
Quoting from the famous Beyonce song, she wrote: "Yep its true, he liked it so he put a ring on it LOL. Celebrating our engagement at Fitzpatrick's Grand Central."
She was instantly inundated with messages of congratulations from her model pals like Rozanna Purcell, Michele McGrath and Nadia Forde.
The Assets model has been dating the handsome soccer star for the past five years and always insisted they were in no rush to make things official.
The down-to-earth beauty said she always knew he was 'the one' for her, but they were relaxed about their relationship.
She's now due to follow in the footsteps of fellow Miss Ireland winner Aoife Cogan with a trip down the aisle herself.
They have managed to keep their romance going, despite her living in Dublin and him being based in Newry, with lots of trips at weekends up and down the M1.
Gorgeous Sarah has said previously that every time herself and PJ went on holiday, her pals were quick to ask if they had got engaged -- always to no avail.
"Everybody is waiting for the day ... I feel sorry for the girls because every time I went away they'd be saying, 'oh you're next', but now they don't even ask. It's so funny," she explained.
One of our most successful beauties, Sarah regularly models at some of the top fashion shows thanks to her super-slim physique and height.
She has also spread her wings in recent years into TV presenting and formerly co-presented TTV on RTE.
She spent three years working for the national broadcaster and said she would love to get back into it again now that she has built up a strong showreel.
"I would like to get back into entertainment, although I am really sporty, so I would love to do a show about that.
"I don't see why more women can't do it," she said.