The 34-year-old singer admitted eight-year-old Flynn - the actor's only child with ex-wife Miranda Kerr - has drastically changed her day-to-day life and she's finally learned what ''adulting'' is all about.
She said: ''We have to be out the door at 7:30 to be there at 8:15 and we cannot be late.
''I used to not wake up until 11 a.m. and now I'm in bed like a normal person at 10 p.m., just like falling asleep.
''I guess this has definitely matured me. I guess this is adulting. That's why I still dress like a child, to fight against!''
The 'Chained to the Rhythm' hitmaker praised her 42-year-old fiance as the ''kindest'' man she has ever met and he is a huge source of encouragement and support to her.
She told talk show host Ellen DeGeneres: ''He is the kindest soul. He is the kindest man I've ever met. He shows up and he's such an encouragement spiritually, emotionally, and physically.
''I do not care to workout and he's like, 'Let's go work out! Let's go do hot yoga!'
''That's kind of our love language is all things spiritual and working out.''
The 'E.T.' singer will have to get used to the change to her habits as Orlando recently admitted he and Katy are keen to have children together.
He said: ''I can't wait to get married again and have more kids at some point in my life.
''That's really important to me but I still feel like I'm growing up.
''Being in this industry, there's so much public attention and you're often flung to the far corners of the world.
''You can spend a lot of time apart and that can be challenging, so I think it's important to make each relationship your own.''
What's new in the music world this week?
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