This is a really difficult group to distinguish!
Firstly,
beautiful is the most emphatic of the three. If
you say, "you're beautiful," you are indicating unambiguously that the
person to whom you're speaking is very, very attractive.
Beautiful is also used as a euphamism to describe some who may not be
attractive at all, but might have good intentions toward others.
This is often referred to as being "a beautiful
person" or being "beautiful
inside".
Distinguish between:
You are a beautiful
woman. vs. You are a beautiful
person.
Pretty is a rather diminutive synonym for
beautiful. Often it is used to describe a more delicate beauty, such as that of children or young adults.
Pretty can also used to describe attractiveness without a lot of sexual connotation.
Nice has many, many meanings, but in the context of beauty
it is fairly neutral. Naturally, a lot will depend on the vocal
emphasis placed on the word
nice. Saying that a girl is
NICE (with a lot of emphasis), may indicate a strong physical (sexual) attraction. Compare:
"Oh, she's nice." (the lack of emphasis neutralizes this phrase for sexual connotation)
"Wow! She's
nice!" (the strong emphasis on
nice sexually charges this sentence).
Others are bound to have more input--these are very subtle distinctions and each have multiple alternate meanings.
C