sounds like maybe the parents need to stop carrying the child around. She's screaming because she knows that they will carry her from spot to spot.

this is what I do, because I've had alot of kids who refuse to walk and would rather scream than walk. I would first do some leg excercises, you will get an idea if something hurts.
then I would do the two hand walk with them. Every time they sat down I would get them back up. Mean I know but it works, they need to start using those muscles. When I'm done changing I would stand them up. Every second I had a chance I would walk with them. then I would move to the one hand walk.

also, get those walking shoes for this kid. they have support on the ankle. Make sure they wear them all day (except sleep) they do help. Also, most places can tell if the child is flat footed too.

and make sure that the child is not in an excersaucer. I had a 13 month old who lived in his and the parents couldn't figure out why he wasn't walking, amazing what happens when you take it away.