Bonnie (29) loved Lottie's big day so much in 2017 that she will almost replicate it when she walks down the aisle of the quaint old St Augustine's church in the village of La Machi, where Lottie's husband Fabio Aprile's maternal grandparents own a house.
Most of the wedding party flew out to Italy on Thursday and many of them are staying in the same hotel the Ryans stayed in five years ago, the Palazzo del Senatore Hotel, in the town of Atina, which dates back to Roman times.
Back then the eldest son of the family, Rex, took on the role of giving away the bride - an honour his tragic father would have been a shoo-in to do before his untimely death in 2010.
Rex, who himself got married in 2018, is set to escort Bonnie down the aisle tomorrow, where she will exchange vows with John Greenhalgh.
Their sisters Lottie and Babette will be Bonnie's bridesmaids, while close friend and fellow influencer Rosie Connolly is tipped to be among the wedding party.
Watching on will be Bonnie's proud mother Morah, who will be accompanied by her boyfriend, singer Don Mescal, and also among the principle guests will be the youngest Ryan sibling, Elliot.
Last month, Bonnie posted online a photo of her wearing an elegant white suit and hat designed by Britain's Nadine Merabi. She also clutched a bunch of flowers at the aftermath of a civil ceremony in Dublin.
Bonnie and John and their guests enjoyed cocktails in the five-star Merrion Hotel followed by dinner in The Ivy restaurant on Dawson Street.
The Italian church she will have her second wedding in tomorrow nestles in part of the Apennine mountain range, which runs down the centre of Italy.
Most of the Irish wedding party will be staying near the town of Casalattico, which is a two-hour drive south of Rome.
This will be the second time Bonnie has attempted to get married in Italy, having cancelled before due to Covid restrictions.
The couple were engaged for just over two years after John proposed in New York in November 2019, and have been together for nearly 13 years since they were teens.
John is northern Europe sales and development manager of Asana, which is a platform that helps teams organise and manage their work and whose clients include Airbnb and Uber.