Mary Page Keller's Sally was definitely portrayed as having put her wayward past behind her. If she had been the version that Julie Philips or Jennifer Runyon portrayed Donna's resistance to her might have been more than snobbery. However I remember there was at least one little nod to Sally's past during Majorca when Sally had to hotwire a car or something and when Catlin commented on it she said that Phil had taught her how to do it. When I found out that Gary Tomlin who was headwriter in 1984 had been playing Morgan Simpson around the same time that Sally was mixed up with Phil Higley that cast that reference in a bit of a new light for me.
I don't think Taylor Miller's Sally behaved as though she had any past whatsoever. She became a pristine princess whom all the Lesoleil boys adored and whose middle class life was so far removed from Catlin's rodeo past that they started to seem fundamentally incompatible. Of course even Catlin's past had been sort of sanitized in 1985 by turning his sort of shady drifter past into a little true love marriage and tragic [presumed] death of his young wife and child.