Remember that Sasha has recently been the victim of unwanted sexual advances from a married man, and is feeling pretty awkward about it. We also don't know about the reason for her scar. She's pretty self conscious at the moment I'm guessing. Ayua in the full is far more of a wild card than before, so the visit to the martial arts studio should reveal a lot between Ayua and Sasha (if she's there. It is important to note that Sasha has her white hair posse, which AYua is part of, so even though Ayua is a Zane, Sasha seems to have a level of dominance in her relationships. Obviously Sasha has a Zane earrinng like Nami does, and Ayua deflects Sasha's questions, so to some extent, both Sasha and Ayua know more than Nami about some important things.
This raises a really important point - most of the women are part of the crowd that know Katie, Leia or Willi. Sasha, Ayua, Bella (knows Zoey, so probably Katie as well - I'm going with the idea that there's more of a rift between Stefan and the Zanes than Zoey and the Zanes, probably Stefan didn't cope with Zoey carrying through with an open relationship with Willi as part of where things all began), Robin (because of Sasha, Layla (whose mom knows the Dean, who is likely to be a Zane or know a Zane) Mila seems to know Ayua well from the start, so we have a picture where almost all of the characters have 1 to 2 degrees of separation from Leia. This raises the possibility that a lot of them are curious about Nami's earring (including unknown bus/pizza goth girl) and that's why Nika is being stalked by Sasha's crew, why the first time are looking into him etc. Nami has the sign of Zane approval/protection, and they don't know why. That earring on a Cyrus 'nobody' puts her in the same category as Sasha. Some of the interest will be curiousity, because Nika and Nami are a mystery to a group that all know each other's pasts.
Also, Ayua is not necessarily an LI, but she has more screen time than Sonia or Marla, so right now she's more 'main' than side. I think Dwight and Aziz will feature more, as will Sai. I think the thing about the characters is, just like Ocean's visual composition, they'll move in and out of focus as the story needs them to, so the standard idea of a background or side character is almost irrelevant.
I'd say we can eliminate some options - it can't be Aziz, unless Molly is Donna's sister. Dwight I think has a good chance of being Sasha's brother. Jake is the character that looks closest to Donna (ponytail guy). But do we even know whether the Revera is on the guys or the girls first team (who got extra time away at the resort)? I'm also guessing Dex and Jazz aren't Donna's kids. Whe also haven't seen Henry, who is mentioned a few times. But even there, we don't know that Donna is the only Revera, she was just the only one we'd seen so far in old WiaB. If Old WiaB is true regards Donna, there's a chance that the Revera on the first time is Willi's sprog.
I'm still waiting for a full quota of reacts so I can like posts again. The site is so frugal rationing them out like this.