This is just a guess, but: I'm going to say that they were her actual mother and father, and that Syla's whole family was corrupted and then killed for it. I'm still going with the "Syla is a seahuman" theory. Just because we have a species name for Syla doesn't mean that she was always a silat. The experiments Tanos was doing on her line up with what Marcus Alderman said about a lab working on curing monsterfication, and we've still got the Vestige of the seahumans calling the MC kin. Plus, Syla describes her fear of lightning being because of the torms enraging the sea and lightning falling all around her, as if she lived on the water.
So where does the "corrupted and then killed for it" part come from? Well, remember that preview image from a little bit ago, of the warrior with electric abilities? I thought that might be one of Indra's spawn, but kibaris pointed out that what look like inhuman features are really just his armor, and he's got webbed hands. So he's probably a seahuman. Meaning the seahumans had a warrior with lightning powers. And if Syla's whole family became monsters, then they would have probably been killed for it. Possibly by the lightning guy. That would certainly reinforce a fear of electricity.
