The 'X Factor' UK judge revealed the media mogul was the first to get in touch following her son Jack's multiple sclerosis diagnosis and insisted he is a better man than people give him credit for.
She told the Daily Mail newspaper: ''He's a good man. He was the first person to contact me when my son Jack was diagnosed with multiple sclerosis.
''He's a big softie underneath it all, a big old softie.''
The 60-year-old star - who is making her return to Simon's talent show after a long hiatus - also denied any rumours of a major rift between the pair.
She explained: ''We've never fallen out seriously. It was just that when Simon said he didn't like working with me I thought, 'Well, I'm going to say something mean about you'.
''Then we spoke and he said, 'Let's stop this. It's ridiculous. We're only hurting ourselves'. And I said, 'I agree'.''
He added: ''He's the biggest kid I know. He's going to spoil that child. It will be the best thing that's happened to him.''
Her parents weren't too fond of the idea.
The flat at Hauptstrasse 155 was where Bowie and Iggy lived between 1976 and 1978 in the city, which inspired the so-called 'Berlin trilogy' albums.
Grint will star alongside Dougray Scott and Ed Westwick in a 10-part TV series for Sony's streaming platform Crackle.
The Brits teamed up at the Hollywood Rose Bowl to perform a cover of The Purple One's 'Nothing Compares 2 U'.