rather loudly

" she says it rather loudly"
What's "rather" here mean? Does have the same use of "very" and "so"? Or it has specific usges?
Could you give me examples?

General_Ricardo,

''So" is an adverb used for "very" as in "I'm so angry."

"Very" means the same as "so" but with more formal use in capacity.

Also "so" means "like this or that."

Also "very" means "great."

... and "rather" can be used in the same way: to strengthen the adjective.

So, I could say: "the party was rather pakked", " the test was rather tough".
Right?

Yes you could. (spelling: packed)