Troian exchanged vows with Suits actor Patrick J. Adams during a camping-themed beachside ceremony in California over the weekend, and guests included the couple's famous friends Chris Pine, Zachary Quinto, Katie Lowes and her husband Adam Shapiro, and the bride's TV castmates Lucy Hale, Ashley Benson, Sasha Pieterse, Keegan Allen, and Ian Harding.
Shay was noticeably missing from the party, and she took to Instagram late on Saturday to explain her heartache at having to sit out the celebration.
"To my big sister T on her wedding day," she began the message, which was accompanied by a photo of the close pals. "I love that we were able to close one very important chapter of our lives together and I am devastated not to be there as you embark on your next one.
"As I sit here thinking about our friendship and journey I am reminded of how much I love, cherish and admire you. I know you and Patrick will have the most special day and I can't wait to celebrate you two as a married couple. Soak it all in and enjoy this moment... it's all yours babe".
Shay did not reveal the reason for her absence, but reports suggest scheduling issues are to blame; she is currently filming new horror movie Cadaver on location.
The 29-year-old didn't miss out on all the wedding celebrations - she was able to help Troian enjoy her final days as a single lady over the summer (16), when the bride-to-be and her best friends jetted off to Europe for her bachelorette party.
Troian's nuptials took place just weeks after she and her Pretty Little Liars castmates said goodbye to the show as they wrapped filming on the upcoming seventh and final season of the drama. The last run of the series will debut next year (17).