You should use the familiar form throughout the sentence. ¿Sabes cómo hermosa eres? - Do you know how beautiful you are? I would also use "ser" instead of estar here - it implies she is intrinsically beautiful, not just a temporary condition.
You know that you want that
It means "You know Spanish, sister."
did you mean usted no sabe? ("you- formal- don't know")
You know that I am in love with you.
Sabe usted.....
Cuando usted dice 'Anade envio y manejo', como sabe usted, si usted no sabe adonde va?
usted ya sabe
No. 'You know' is "usted sabe." If you said, "Ella me sabe," you would be saying, "She knows me." But the kind of 'know' this is is the academic kind, not the empirical, experiential kind.
Que sabe usted/sabes? (formal/informal)
Sabe usted/sabes coser? (formal/informal)
sabe usted/sabes ingles? (formal/informal)
mi mejor amigo - my best freind