Sandi is self-centered and concerned primarily with keeping herself at the top of the popularity pecking order, placing her head-to-head with Quinn on a regular basis. There's a serious rivalry between them that lasts the entire run of the show. This rivalry is reflected in the way Helen and Sandi's mom Linda relate to each other. Sandi speaks with an odd accent which is reminiscent of a Valley Girl dialect, though it sounds fake.

Naturally, as President of the Fashion Club, Sandi's primary concern is keeping her wardrobe and style up-to-date. She also insists that girls shouldn't play sports, an attitude shared by the rest of the club. She rules the club with an iron fist, keeping control over the other members by various means, controlling Quinn by means of subtle threats and the invention of new rules as she goes along, Stacy through sheer intimidation, and Tiffany through no significant effort at all.

Sandi takes satisfaction in watching Quinn fall, and often sets her up for it. One particular occasion involved getting Quinn to volunteer for a dance committee - a job that Sandi knew from experience was a bad idea. When she was younger, she volunteered for a similar job only to have the whole thing go south, mostly due to her brothers (Sam, Chris) ruining everything. Quinn will occasionally return the "favor", and set up Sandi for humiliation (though she's not as good at it). Sandi feels that she holds something major over Quinn with the information that Daria is her sister, not her cousin as Quinn usually insists, but it turns out everyone already knew. In spite of all this conflict, Sandi considers Quinn to be her best friend.

Sandi had to wear huge braces while she was in fifth grade - a fact that she seems to have been able to keep secret from nearly everyone, indicating that she wasn't living in Lawndale at that time.

She drives a yellow convertible, though it's not clear whether it's actually hers. Though in the same class as the rest of the Fashion Club, she may be a year older because she is able to drive while Quinn is still only 15.

Sandi has a weakness for cute babies - one wonders if this is a new development, or whether her relationship with her younger brothers started off much better than it is now.

During the Homecoming Parade, she gets in a fight with young Tad Gupty, who calls her a mean old witch. Sandi insists that she is not old.

On one memorable occasion, Sandi gave Helen a makeover (much to Quinn's embarrassment) and was actually on first-name basis with her for a bit (again, much to Quinn's embarrassment). The makeover came out a little overdone, which may be because Sandi make it look bad on purpose, or she may simply be no good at it.

She claims to have an undisclosed condition that requires her to sleep in Quinn's bed instead of the floor during a Fashion Club sleepover party. Knowing Sandi, she more likely just wanted the comfy spot for herself.

Sandi once fell and broke her leg, and during her recuperation gained a significant amount of weight. Too ashamed to show herself, she resigned from the fashion club and was ready to give up before Quinn pulled her out of her rut and got her back in shape. Sandi was so touched at this show of friendship that she cried on Quinn's shoulder. This event also marked the beginning of the end for the fashion club, as Sandi began to lose her power. She does actually mellow out considerably after the experience, becoming more gracious and willing to entertain her friends' opinions.

During their junior year, Sandi and the Fashion Club published the Fashion Club Forecast, a newsletter which ostensibly predicted upcoming fashion trends - except that they get everything wrong. Undaunted, Sandi hung a plaque for the Fashion Club in the girl's room at school, a plaque which reads "We Mean Well".

At the close of her junior year, Sandi developed a protracted case of laryngitis - much to Stacy's dismay, as she had used her birthday wish to wish that Sandi would shut up. When Sandi regains the power of speech, she prepares to hold this over Stacy's head in a big way, but it turns out that Stacy would rather quit the club than go along with Sandi's dictatorship any further. This kicks off a minor chain reaction in which the remaining members also quit the club until Sandi is the only one left - whereupon she quits too, and thus endeth the Fashion Club.