There are actually two types of sign language. ASL- the most common, American Sign Language, which uses individual signs for words and phrases. SEE- which Aubrey uses, Signed Exact English, (from here on out SEE) is where the signer uses a sign for each word in the English languages, much like you would see written or hear from a speaking person. So the phrase "It is nice to meet you." in ASL has three signs. In SEE you would sign 6 individual signs.
The benefits to her learning SEE is that it will help her in school, especially with learning to read and write and learn proper English. In the future when she sits down to write, she will be able to put together a complete sentence and have it make sense to her readers, instead of writing down one word to represent a phrase. Make sense?
Aubrey got hearing aids two years ago, and we have learned hundreds, maybe close to 1,000 by now, of signs to be able to communicate with her and also understand her wants, needs and emotions. Our sign language is "choppy" and slow, but she understands and we understand and we are learning more and more each day.
When your 4 year old kid knows more than you...it's time to enroll in school and get ahead or at least keep up! Class is for another post though:)