Remember what he said? He puts Ink in his eyes to make them look like a ghouls! That way, no one would question it!
Plus, when he was hanging out with Yomo and Arima showed up, Yoshimura saved Yomo but left Uta (And his gang) with Arima and they survived? Ridiculous!
Just because she has a strong kagune doesn't mean she is strong. I would be extremely surprised if she is stronger than shachi.