It's already been prayed for!

My daughter Faith loves to pray. A great thing. But one of the funny things is that if myself or Jake pray first and we hit on something she was going to pray about she'll throw a major pointy and give off!

This happened the other night as we read that days Operation World and Jake prayed for the country and its people. Faith broke in "JACOBBB!!!!! . . . .I was going to pray for Romania"

When you tell her it's okay and she can still pray for them, she'll disagree and will say "it's already been prayed for!"

I think i'm going to teach her that the proper response and how to express that you are raging with someone for praying what you were going to pray is to loudly shout "AMEN"

Each time this happens I keep thinking how her sentiment is spot on, it's already been prayed for. Do we need to repeat what the person praying before us has just asked of the Lord? I'm not saying it's necessarily wrong, but just asking why.
Or could we say amen with them as they pray and then bring other thanksgivings, supplications and petitions before the Lord?