We don't even know her last name, but somehow she's worked her way into the family. When she says she might feel uncomfortable staying after Judith goes, Jean appears to be heartbroken. She tells Sandy that she's like a second daughter to her and that's exactly how she treats her. When Alistair wants to discuss something that might have been perceived as "for the family only" Sandy excuses herself and starts to leave. They insist that she stay -- provided she doesn't call Lionel daddy.
And she seems to have found her way into that tough heart of Lionel's. He's very protective towards her. He really has a problem with the thought of her as a St. Trinian's girl and he meets with Harry to discuss his concerns. He follows Sandy and Judith to the street market just in case her stalker should show himself. There's no way that one could mistake her for a boarder.
Sandy is a clever girl who is very good at what she does. Jean, who never considers Judith for the job of Branch Manager, doesn't seem to have any hesitation about picking Sandy. She knows the business in and out and can run the office as well as perform the secretarial duties in a pinch.
No way that she's a hardnosed business woman, though. She's a sensitive person. One who has probably cried more than anyone during the run of this series. She cries at weddings -- we've seen her at Lionel & Jean's and also at Rocky & Madge's. And she really was torn when Alistair offered her a job at what obviously was a much higher salary than Jean could ever pay. She thought about it and the thought moved her to tears because she felt she was being disloyal to even think seriously about it.
She's not been divorced twice, but she's giving Judith a run for her money in the suitor department. There don't seem to be too many requirements for getting a date with Sandy. I guess that must mean that she's not all that fussy about her relationships. True, she was going steadily with Nick when we first met her. And they had some problems and split, but were reunited. The togetherness lasted only a short time and it was their breakup which ultimately led to Sandy's moving in with Jean and Lionel. And to a string of ill-fated relationships -- ranging from a man who was too fond of Rugby to a man who was too fond of pain. She's had quite a few spontaneous dates -- from a biker/poet with whom she shared a good cry to a group of six brothers who courted her as a unit.