The Duchess of Sussex will always be ''so grateful'' to Oprah Winfrey for befriending her mother.

The media mogul reportedly offered support to Doria Ragland when the former social worker became overwhelmed by the attention she received as a result of her daughter's relationship with now-husband Prince Harry, and Meghan feels ''comforted'' knowing her mom can turn to the 'Wrinkle in Time' actress whenever she needs help.

Authors Omid Scobie and Carolyn Durand wrote in new book 'Finding Freedom':

''Doria found an unlikely ally in - of all people - Oprah Winfrey.

''The former talk show host, who had been introduced to Meghan by a friend, reached out to Doria to offer her support when she was first swept up in the media storm. It turned out that on occasion they went to the same church, the Agape International Spiritual Center in Los Angeles.''

A source told the book: ''Oprah has been a friend and a help to someone who's been in a pretty extraordinary situation.

''There are not many people who can understand the situations that Doria's found herself in, so it's great to be supported by someone who understands the pressure of being in the public eye...

''Meghan will always be so grateful to Oprah for being someone her mother can turn to.

''Doria has plenty of friends, but there's a comfort you can take in knowing that someone like Oprah is close by and supportive.'''

However, Oprah reportedly faced questions from royal aides about her intentions behind befriending Doria.

The book reported: ''Doria was able to spend time with Oprah when she needed to get away from her house without worrying that she would use their friendship to get an interview.

''A senior palace aide had an honest conversation with Oprah before the wedding, where she assured them that 'that's not what any of this is about.'''

The writers admitted they found it ''so interesting'' that the former talk show host faced questioning.

Omid told 'Access': ''I found that so interesting because no one on earth should ever question Oprah's motives. We always know that it comes from such a great place and I remember hearing from a senior aid at one of the households that they had had a conversation with Oprah to make sure that her intentions with her friendship with Meghan and Doria came from a good place, that she wasn't just trying to get an interview.

''I think we've seen Oprah really prove herself to be a very respectful friend, she's said very little about any of the Sussexes in that time.

''And, listen, I think that shows just how protective the institution is of any newcomers coming in, no matter what your background.''