Japanese sentence...

をうしてみつけた　あんたが　いちばん　～
This is not a complete sentence, it should have something before”を”、I think it is a part of a script, the usage of を must have object before and verb after,

for example,
林檎を食べました。
I ate an apple.

I think the meaning of this sentence is that
"Great, You have found something"
something or XX をうしてみつけた　あんたが　いちばん　～