Sophie, who described her style as “rock & roll maximalist” said the designers all felt the pressure of creating something within a time limit and budget each week.
“It is stressful but it’s the most fun I’ve ever had.”
She said she had discussed what happened on the programme with their “nearest and dearest” but overall it had been a “hard secret to keep”.
She and her fellow competitors have been able to watch the first episode.
“It’s really good fun. It’s funny. I’m excited for everyone to watch,” she explained.
She said presenter Carr was “the loveliest guy”.
“Exactly what you see on TV is exactly how he is. He’s just a delight,” she added.
She said seeing him come to visit them during their work on the programme “instantly cheered you up”.
“He’s a lovely guy to have around,” she added.
Interior Design Masters is on BBC One on Tuesday at 20:00 BST.