What does a 17 yr old need to cross the border into canada that isnt traveling w/ parents but w/friends?

we are going to canada for a little summer trip and everyone is 19 except for one person who is 17, she has a birth certificate and her photo id and her parents approval, what else does she need to take to be able to cross the border?

a note from her parents saying she can travel with the friends, listing all the friends full names. and signed by parents. also a passport wold be better. some border crossings won't accept birth certificates anymore.
i live 20 min. from the canadian border & go there quite a bit.
a note is very important!
have fun!

Slightly is right, You need a note which might need to be notorized (any bank can do that for free) and a valid passport.

Have fun!!1

She will definately need a letter from her parents..as well as their telephone number as the border patrol will call. She's going to need a passport. . along with all the i.d she has.. she may also need a copy of immunization records.
I just went through this a few months back with my 17 year old.