Princess Kate Middleton and Prince William’s designer friend, Amaia Arrieta, says she’s “heartbroken” as the royal couple cope with the princess’ cancer battle.

“I’m heartbroken at the moment. I think they are going through hell,” Arrieta said in an interview with The Telegraph published on Thursday, May 2. “I hope they will be back. It’s really personal.”

For over a decade, Arrieta has worked as the stylist for Kate, 42, and William’s children Prince George, 10, Princess Charlotte, 9, and Prince Louis, 6. She began dressing the little ones when George was born in 2013 and has continued to work with the little ones’ nanny, Maria Teresa Turrion Borrallo, to style the children for their various royal engagements.

“It’s often a very tight deadline,” Arrieta told the outlet. “We would do anything for them … the children always look amazing in the end.”

Arrieta gushed that getting the opportunity to dress the royals fills her with “so much pride” and she really cares “about how they look.”

Charlotte recently wore one of the skirts Arrieta designed in a photo that Kate and William, 41, released for Mother’s Day in the U.K. in March. The picture was the first official shot released of the family following Kate’s abdominal surgery earlier this year. At the time, the portrait was flagged by multiple outlets for being “manipulated.”

Kate later shared that she edited the photo and apologized for the confusion. Nearly one week after that, Kate announced that she had been diagnosed with cancer.

“I wanted to take this opportunity to say thank you personally for all the wonderful messages of support and for your understanding whilst I’ve been recovering from surgery. It has been an incredibly tough couple of months for our entire family, but I’ve had a fantastic medical team who have taken great care of me for which I’m so grateful,” Kate said in a video. “In January, I underwent major abdominal surgery in London and at the time it was thought that my condition was non-cancerous. The surgery was successful, however, tests after the operation found cancer had been present. My medical team therefore advised that I should undergo a course of preventative chemotherapy, and I’m now in the early stages of that treatment.”