Holmes, who filed for divorce from the actor in June, has said that Suri is still adjusting to a much more modest lifestyle, reported Us magazine.
"She said the divorce has been hard on Suri and she's acting out," a friend of Holmes said.
But the 33-year-old actress is determined to remain firm and not give in to the elementary schooler's every wishes.
"Katie says no to some things, but gives a little leeway. She knows Tom is going to spoil her," the insider said.
Suri is famous for her million-dollar wardrobe and has been named one the most fashionable star kids time and again.
Earlier this month, she started school at NYC's elite Avenues, where she'll have to swap her designer heels for Lands' End uniforms per the strict dress code.
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Holmes, for her part, is thrilled about the opportunity to encourage Suri to wear more casual looks.
"She wants [her] to fit in and be more of a normal kid," said a source.