[blinker12]

To my ears, both "Not Make Believe" and "Silver Girl" are pretty standard-issue Stevie songs. Not terrible, but not great either. Certainly, with lines like the ones people have already mentioned, it doesn't seem that Stevie was taking much care with the lyrics. ("It hurts my self-esteem/It hurts my everything" is a particular groaner.)
That said, I would have preferred "Not Make Believe" to "Silver Girl." First of all, I think the chorus is a little catchier. Also, I like Lindsey's production on NMB better. It's crisper and less blobby _ more guitars, fewer synths.
Both songs benefit enormously from John and Mick's rhythm playing. Their bass and drums give the songs what little backbone they have.
If I had to speculate on why "Silver Girl" beat out "Not Make Believe" _ I bet Stevie campaigned for the former. It probably has more personal meaning to her, and she probably wanted to make sure her tribute to Sheryl got out to the public.