The former Pussycat Dolls singer adores her friend and ex-bandmate's little girl Willow and even though the tot is only six months old, she is already planning activities to do with her.
Kimberly said: ''I've never seen [Ashley] so excited about a child before. The spark is ignited within her!
''We were hanging out at Ashley's yesterday and she asked, 'How soon can I paint her nails?'
''Ashley is probably the person I've been closest to in my life. We spend as much time together as we can.
''Being a mum keeps me at home, so we can't go on girlie nights out but we have movie days.''
The 33-year-old singer - who is married to model Max Rogers - would ''love'' to have a sibling for Willow, but has no plans to expand her family in the near future.
She told Britain's Star magazine: ''I'd love a brother or sister for Willow, but we won't start trying any time soon.''
The 'Got To Dance' judge admits her priorities have taken a ''huge shift'' since she became a mother.
She said: ''Your priorities take a huge shift [when you have kids]. It's all about Willow now and it takes a good reason to get me out of the house.''