Lady Azura

If only I knew how to link to gifs...

I feel like you know Zoe's into her sometime when they're at Lola's Canteen. When Grace gets up to get another drink, Zoe watches her leave with some dazed, longing expression. This is right before Miles suggests that Grace has been "hanging onto [her] every word" even though, from an audience perspective, Zoe's been the one doing that.

I think Zoe herself realizes it after they have the talk about love and Grace is all jokingly like, "Maybe you're the one in love with me."

With Grace, it's harder to pinpoint mostly because Grace is hard to read in general. I'm going to say around the time Zoe ditches her to hang out with Miles -- she seems genuinely upset about it, especially when they're at the Hollingsworth house and Zoe is apologizing/inviting her to the Full Moon party.