What is the significance of Risa in Unwind by Neal Shusterman?

Risa is one of the three main protagonists of Unwind.  The other two are Connor and Lev.  Risa is significant to the story because she gets just about a third of the book told about her.  She's more important to the story than mere page counts though.  I think Risa is quite significant because she is able to temper quite a bit of Connor's impetuousness.  Connor often doesn't think things through.  For example, when Connor rescues the storked baby, he has no idea what his plan is.  Risa, as the story continues, is able to get Connor thinking things through before he acts.  In literature terms, she is a foil character to Connor.  
Risa is also significant to the story because she represents Connor's only true friend for much of the story.  Lev doesn't appreciate Connor's rescue until very late in the story.  Connor's girlfriend isn't willing to stay with him because he's an Unwind.  Roland wants to kill Connor, and everybody else either backs Connor or Roland like they would back a prize fighter.  They just want to support a winner.  They don't necessarily care for or even like the person.  Risa is the only one who chooses to stick with Connor because she sees the person that he really is, and she likes him for it.  Lastly, Risa is significant to the story and the Unwinds in the Graveyard because she quickly becomes one of the go-to medics for everybody there.