Speaking to British newspaper The Sun, James reveals she has supported him when he's battled anxiety issues that sometimes make it difficult to perform on stage.
"We're in touch all the time, she's so supportive," he explains. "Any gig she can make, she's there like a proud mentor."
The pair have also been keeping each others' spirits up during lockdown, and are even working on new music.
"I'm working on something with Nicole right now," he adds. "I can't say what it is but I think it's going to be a nice surprise. We got our heads together and thought, 'How can we entertain fans during this lockdown?' "
Meanwhile, the British star is writing the follow-up to his hit 2019 album "You", which he says will be a departure from the romantic ballads which have made his name.
"I want it to be a massive departure from the middle-of-the-road pop that people hear from me on the radio," James muses. "I'm not really bothered whether the radio picks stuff up any more because it seems like they only want to play stuff that sounds like (his 2016 hit) Say You Won't Let Go."
James has also released a new acoustic version of his 2016 track "Safe Inside" to mark the U.K.'s Mental Health Week, with proceeds from the single going to mental health charity Sane, which he is a patron of, and the NHS Charities Together Covid-19 appeal.