I still maintain that Sally has always had delusions of grandeur in some way or another, whether
that's openly trying to improve herself and her family or being quick to try and silence people who think that she is common. In her first episode in 1986, Sally compares Hilda's house to her own family home, pointing out that Hilda has wallpaper whereas her parents don't. From the outset she is shown to want more for herself. In the same episode she is quick to jump on Hilda when she comments that Sally is from a rough part of town. Sally hits back: "We can't all live in Tatton Hall, can we?".
The problem was that Sally had two awkward periods in the 90s and early 00s that changed perceptions of the character. From about 1993 - 1997 she was a drudge of a housewife to Kevin, always fussing about the girls, telling them to wash their hands and serving up fish fingers. She had some brief involvement in stories that saw her start working for Mike Baldwin in his factory and wanting to progress to management but they fizzled out in the run up to Kevin's affair with Natalie.
1997-99 were vintage years for Sally, with Kevin's affair and the breakdown of their marriage and, later, her involvement with Greg Kelly. This was underpinned by her working for Mike Baldwin at the factory and taking on a more senior position, which allowed Greg to manipulate her into helping with his schemes to ruin Mike by stealing business contacts.
Then, from about 1999 - 2001 Sally lost her way again by being given jobs that just didn't fit the character at all. At first she became a market stall trader and then went on to open a hardware shop. Both of these periods didn't fit with the character one bit.
From 2001 onwards, after she was reunited with Kevin, the 'original' Sally started to reappear and that's when the character we see today started to really develop. Disappointingly, her social climbing traits have become much more simplified over the past 3 or 4 years which has turned her into a very one dimensional caricature.