I *feel* like I've read every SLIDERS fanfic ever written. I honestly don't remember ever seeing Michele in any stories although that doesn't mean there weren't any.
Michele's situation is odd: after "Luck of the Draw," Torme wanted to have Ryan and Henry stay with the sliders for several episodes. FOX refused to allow this, saying it would lock the network into a specific airing order for episodes. Fox didn't even want the Season 2 premiere to so much as mention the cliffhanger. Torme had to fight until finally, FOX permitted him to resolve "Luck of the Draw" in a teaser attached to "Into the Mystic". This would indicate that Torme would have known that Michele featuring in an episode after "El Sid" would never be permitted.
However, this doesn't seem as clear cut because "El Sid" has a production code of K0802. "Time and Again World," filmed first in Season 2, has a production code of K0801. "Into the Mystic" has a production code of K0807 and the aired teaser was filmed significantly after the rest of "Into the Mystic" was filmed and edited.
Sliders-expert Temporal Flux reports that FOX set press outlets videotapes of "Into the Mystic" that didn't have the actual teaser because it hadn't been edited into the episode yet and attached a letter effectively saying, "We know the episode doesn't resolve the Season 1 cliffhanger, it totally will by the time we air it!"
I guess it's possible that the creators, having not yet won or lost the battle to have Ryan and Henry in more episodes, saw Michele as another character who could conceivably feature in an episode after "El Sid." However, it's also possible that Michele's arc was meant to conclude with her defeating Sid and free to choose her own future on some other world and that any Earth on which she'd remain would be better than any life with Sid.
There seems to be a factor of rushing and not thinking during this period of SLIDERS. Torme noted that "Time Again and World" was shot first and confessed that it was done in a huge rush with the writing team and crew not ready to start filming again, leading to scripting and visual errors throughout this episode. "El Sid," shot second, is another episode Torme describes as suffering from this urgency, calling it two-thirds of a story padded out to fill a timeslot, and the episode seems to bear this out with too few scenes, all of them significantly overstretched beyond what is needed for the content within them.
The production drafts also seem strangely indecisive about the Michele character and also how the story is to end. Michele's character in early drafts beats Sid into submission with a billy club at the end, leaving him alive (until the earthquake gets him) and then Michele slides with the quartet. It's an awkward situation because it's unlikely Michele would reappear, and a subsequent draft tries to amend this where Michele shoots Sid, but with his dying breath, he stabs her in the back and she dies; the sliders depart and leave Sid and Michele's corpses lying side by side as the ceiling collapses upon them.
This was clearly too bleak and depressing, so the writers settled on keeping the rewrite where Michele shoots Sid and frees herself of his abuse but maintaining the original conclusion where she slides out with the others. It looks like this is where they had to leave it and start filming; it's probable that production simply ran out of time to figure out how to have the character exit the episode and settled for the draft they had. If FOX could be persuaded, Michele could appear in the next episode; if FOX were firm on no set airing order (and they were), then Michele presumably parted ways from them between episodes.
This wishy-washy, middle-of-the-road strikes me as the product of a situation where, as Torme notes, "El Sid" was a severely short, rushed, overstretched teleplay pressed into filming before it was ready.
There's another discontinuity of sorts in "El Sid." This episode continues the thread of "Luck of the Draw" where Quinn and the Professor establish that the timer is already strained to the limit in creating a gateway for four people; introducing additional sliders could cause the tunnel to collapse on them in mid-dimension. "El Sid," filmed second, was continuing a plot element introduced two episodes ago. But it's permanently discarded after this. The sliders and Michele slide and at least four of them are fine afterwards. Wade drives a truck through the vortex in "Love Gods" (which aired before this one and also had extra sliders who are never seen again).
A later script was supposed to have Geraldo Rivera slide with the gang and suffer no harm (from the vortex, anyway). In later seasons, the sliders regularly take extra sliders and drive vehicles through the gateway without concern. I suppose the implication is that Quinn's system, while thought to be limited, turns out to have infinite capacity aside from the (supposed) 60 second window that the vortex can stay open (although it always stays open for as long as the plot requires!).