You are a very Pretty Girl
I wouldn't use "prettiness" in a sentence because it sounds awkward. I'd use "beauty" instead.
That is a very pretty touch-me-not.
That gecko was pretty cool.
some weavers are pretty good at weaving
I bet Nike are pretty chuffed to have them both.
She is wearing a very short miniskirt, but it is pretty.
It was a chartreuse color, pretty and exquisite.
The flowers were as pretty as sparkling diamonds.
I found some pretty zinnias by my house
These earrings are very pretty. This dress is nice.
An opinion is a personal view, essentially. An example sentence would be: His opinion was pretty offensive to everyone there.