Which Donna? The one who does not remember? Or the one who does? And which Susan? The obvious angle would be that Susan feels envy of Donna who so easily forgets and so doesn't go through the pain that Susan herself does as she strives to forget. Yeah, I don't think so either.

Or the remembering, empathetic, embracing Susan who feels enormous sympathy for Donna who, unlike Susan herself, can never remember the wondrous things experienced. Yeah, I don't like that one either.

Or, something more like the following:

"I was almost married, once," Donna says offhandedly during their coffee break as they overhear two other office girls twittering about an upcoming wedding.

"Oh?" Susan asks politely stirring her tea in the vile paper cup. Donna does not sound especially broken up about it. Susan admires her competence and though Donna is accustomed to always being being dismissed, Susan takes offense at this on Donna's behalf. Excelling at management is a gift and Donna's employers are fools to not see her skills. It might seem prying, but Donna does not mind, so Susan asks, "Was it a mutual parting of the ways?"

Donna shrugs. "He was the front for an alien plot to take over the whole world."

Now that Susan can empathize with readily. "Men," she says with a little grimace of disgust, "always looking for women as a means to fulfill their bigger plans."

"Exactly!" Donna says. "If they let us in on these diabolical plots we could talk some sense into them!"

"Or at least their diabolical plots would be better organized," Susan concludes.