Not knowing the lyrics to a song you're about to perform is unforgivable. Especially if you did guest vocals on the album version. And about her vocals, it's all been said before I think.

shes pretty hot in person.. i'll give her that

Could've been better, it clearly wasn't rehearsed at all. My guess is it just randomly happened. Not knowing the lyrics is understandable too; it's not her song, she did some guest vocals for the acoustic version, but she probably used the lyrics then too. Ryan's the one who is the guest here, not Cassadee as well.

They both were kind of off, but that's expected when it's just randomly done.