Pretty: A woman with a lovliness to her pyhsical appearance (used for almost all women who are not my SO but are visually apealing).
Hot: A woman with a come-hither appearance and a body to attract attention for at least a brief moment (but not much else. I rarley use this descriptor).
Beautiful: A fine combination of the two above, along with a kind of inner being that is attractive. (this is the one I prefer for my love.

)