Hola Dawn,

Curiosa= nosy. So, Cristina es la más curiosa de mis amigas. She is the nosiest of my friends.

Ruidosa= noisy. In this instance you would write, Cristina es la más ruidosa de mis amigas. She is the noisiest of my friends.

Hope this helps :)

Oops. Thanks. I didn't catch that there was only one i.