and let's not forget, Seven Wonders is NOT really a Stevie composition at all. It was a Sandy Stewart song in which Stevie mis-sang a few words and for that demanded listing as cowriter and got it.
So really, all she brought to the table was two songs --Welcome to the Room Sara and When I See You Again. And of course the Sandy Stewart song was the only one worthy of being a single (so if you're SS, who had to give 25% to Stevie, it would seem 75% of a Mac hit is better money than 100% of nothing). (Also interesting to note is the vocal on the released version of Seven Wonders is a slightly sped up version of how she actually sang it... slower and a bit lower. It would seem they either couldn't get her back in the studio for another take, or they couldn't get a better take out of her and had to fiddle with the one complete good take they had).
Stevie got really shady about how much her writing was petering out as time went on, and many of the songs that were Mike Campbell musical tracks that she put lyrics to were not credited as such on the actual album credits at the time. Shady.