I ignored Zenda my second play because I wanted the mini-harem, but I remember her from my first play and also found her very sus. I wonder if there is more to her in the story as we progress.
There might be more to her, but I don't think it's anything sus related to the big story arc, because she's pretty much absent from the game, if you're not on her path. She doesn't chase after the MC and if you don't make time for her she straight up ignores the MC at the gym, which is the last time you'd see her.
If there's more to her, then I think it's that she's more romantically inclined than she's letting on. The power dynamics between her and the MC are very much in her favour and she's got a lot to offer and does so casually. All of her scenes so far have been pretty adventurous. But I think she's not just in it for the adventure, but is also very much into the MC.
In the last scene of the current update
she's not really jealous, but sad, if you go for the threesome. I feel like, even though the sex scenes with her are pretty adventurous, the relationship with her is going to be a more down to earth monogamous romance.
It seems like she wants the MC to claim her, just like she's claiming the MC, because she prefers the intimacy of a twosome.