Hi we leaving next week Saturday to Iowa with my kids but one of my passport it’s expired can she still able to fly ??

No. It must be be renewed if your leaving the country

If it is your only form of ID for travel is must be current.

A passport is not required for Domestic Travel. If you want to travel Internationally, you will need to renew your expired passport first.

To some Iowa maybe "out of the country" but it isn't. Yes, she can use it.