Reese: Vince is a Child!

She’s Type A, and he’s old school — no wonder and Vince Vaughn didn’t get along while filming their holiday comedy, Four Christmases.

According to a friend, Reese is dreading the movie’s promotional tour with Vince, whom she describes as “the biggest child I’ve ever met!”

“Promoting a movie involves long hours, and she’ll have to spend a lot of time with someone who gets under her skin,” the pal tells OK!.

“Reese is professional — she’ll grit her teeth, fake a smile and pose for pictures — but she’s not looking forward to it.”

Reese has also asked her ex-hubby, Ryan Phillippe to care for their kids, Ava and Deacon so she can keep her cool with the other child in her life: her co-star.

Reports of tension emerged from their film set late last year with perfectionist Reese even speaking out about the freewheeling ad-libber.

“I said to him one day, ‘People can’t talk as fast as you think.’ You can’t keep up with him. But I feel like I’ve been in training — Vince Vaughn training!”