The 'Bleeding Love' singer – who first shot to fame after winning Simon's pop star search show 'The X Factor' in 2006 - says Mezhgan Hussainy is a wonderful person and she is really pleased her mentor is finally tying the knot.
She said: "She has the Leona Lewis seal of approval. She's lovely."
Leona is in a relationship with Lou Al-Chamaa - who she has been dating for five years since before she was famous - and insists she would always choose her man over her career.
She said: "I love of music but, or course, I'd choose love over that. For me, love is happiness and inspiration. But I mean the love of my life and the other love of my life go hand in hand."
Leona insists she is really happy with Lou but doesn't like to talk about her love life.
The 25-year-old pop star added: "I always try to maintain my private life. My private life is the most precious thing to me."