Originally Posted by SCORGE
massage baking soda into the cushion, vacuum out, repeat till odor is gone
This will work. The wife had a cat that had a bladder infection, and the cat kept peeing on one spot of carpet. She coated the spot with baking soda. It absorbed the moisture and smell.
In this case however, you may need to "re-wet" the spot for this to be effective. I'd go the route of having the cloth seats steam cleaned by car detail shop. Then lay down some plastic (buy a role at any hardware shop) under the child's car seat.
Or buy a cheap plastic seat cover.
Give your daughter a big kiss though; this stuff happens. No worries, as a car seat is no big deal.