The dressmaker, who created Kate Middleton's flower girl dresses for her 2011 royal wedding to Prince William, has also made creations for royal families in the Middle East.
And for the first time ever, her work will be available in Ireland at Brown Thomas, Dublin.
The designer's First Holy Communion Dress collection has just been launched in the Grafton Street store and Ms Macfarlane will on hand on February 1 for "one-to-one appointments with customers", a spokesperson for Brown Thomas has said.
Ms Macfarlane said: "This time of year the diary is full with Irish business and we joke that we could hire a plane we've so many customers coming from Dublin.
"Irish people have been coming over to me for several years." Customers either buy from her ready-to-wear collection or else they have a dress especially created for their special day.
For a bespoke Communion or flower girl dress, prices start from £450 (€550).
She has also created designs for high-profile people in Ireland, but won't be drawn on exactly who.
"The royal wedding made things happen for us a lot faster. It was a lovely thing to happen to us and it certainly put the business in the spotlight," the designer to the stars said.
Even though she's used to dressing the darlings of royalty, she has a soft spot for her non-celebrity Irish clients.
"Irish customers are great fun, their daughter's first Holy Communion really, really matters to them and they're very involved," she said.
Brown Thomas in Dublin will carry her collection plus two exclusive dresses which are full of "glamorous sparkle", the store said.