Meghan Markle and Serena Williams have been "relying on each other a lot recently".
The Duchess of Sussex and the tennis star have known each other for a long time but she says they grow closer and closer by the day.
She said: "We were actually just texting each other this morning. We have known each other for a long time, but we really are relying on each other a lot recently."
And Serena felt like she was "watching history" when she saw Meghan tie the knot with Prince Harry in Windsor Castle earlier this year.
She told Australia's The Project: "I felt like we were literally watching history. I feel like in a few years, when I look back at that moment, it's just gonna be so historic. It's gonna be something people never forget. The whole service was really wonderful and most of all, I just wanted to see my friend be happy and I think that's what happened."
Meanwhile, Serena previously revealed she feels "proud" of Meghan, Duchess of Sussex after she launched a cookbook in support of the victims of the Grenfell tragedy.
The 37-year-old royal has written the foreword to a recipe book from cooks at the Hubb Community Kitchen, which is based in London.
Responding to the announcement, Serena wrote on her Twitter account: "I used to call you Meghan (and I still do) but dear Duchess of Sussex your first project "Together" a cookbook bringing women of all cultures together. I could not be more excited about it and proud of you. It's beautiful - diversity, inclusivity, coming together in grief or joy (sic)"