"Mirror Mirror" was a separate project from "Rock A Little"...Stevie was unhappy with "Mirror Mirror" as whole and decided to start over with new songs this became "Rock A Little"...If Stevie had not scrapped "Mirror Mirror" it would have been her 3rd record and "Rock a little would have been the 4th
An excerpt from her wiki page...
Following the tour for The Wild Heart, Nicks commenced work on her third solo album. Originally titled Mirror Mirror, Nicks recorded songs for the album during 1984. However, Nicks was unhappy with the album, and opted to record a new batch of songs in 1985.[55] Rock A Little, as it was re-titled, was released November 18, 1985 to commercial success, supported by three successful singles.
Stevie Wiki
Back then Stevie had things planned out 2 or 3 records in advance...Perhaps FM should of put Stevie in charge of things back then maybe they might have made more records...