"She is not excited."
Translation:Dyw hi ddim yn gyffrous.
My dictionaries give "cyffrous" as "exciting" rather than "excited". Is it used for both?
It can be. As with other terms and expressions, there are other ways of saying it, but this one is simple and commonly used and understood.
How would you say "excited" if context wasn't going to make clear you didn't mean "exciting"?
I'd stick with cyffrous, I think... If somebody was excited as in 'agitated' then perhaps cynhyrfus/cyhyrflyd/berwedig. If excited by something, then maybe even wedi cyffro/cynhyrfu.
In the wild it doesn't really come up as a problem - there is a context of some sort.