The former Miss Ireland and her rugby player beau have called it quits, Holly confirmed to Independent.ie
The loved-up pair, who first met while protesting for their local community in Clontarf, are keeping the details of their split private.
Holly and Cian, who bought an adorable pug Ted together last year, are just back from their plush Spanish holidays last month.
And earlier this week, Holly and model pal Jayne Higgins have embraced the VIP party circuit as they attended the celebrity filled golf fundraiser for the Marie Keating foundation at the K Club.
The pair have also just booked a girls trip to Marbella.
This has been a summer of change for Holly as she recently switched from Andrea Roche Model Agency to Assets and she's also working full steam ahead of her lifestyle blog.
She has also turned her hand to acting as she made her comedy debut in Oliver Callan's Friday night show, Callan's Kicks.
The mimic couldn't help poking fun at the whole Garth Brooks fiasco as he enlisted the services of Holly to help him make a parody of Nathan Carter's biggest hit Wagon Wheel.
The country star was due to support Brooks at two of his five gigs in Croker with the show airing on the same night as one of the cancelled concerts.
In a setting that's a far cry from her usual glamorous hang-outs, the model posted a picture of her dressed in a checked shirt with some cows in the background.
"I'm the love interest in a parody country music video," Holly told the Herald. "We're filming on a farm in north county Dublin and it's going out the day Garth Brooks should have been playing Croke Park. It's on Friday in the Late Late slot."