I can’t decide on an interpretation for this moment.

On the one hand, Rei is completely new to the having friends thing. She has the children who come to the shrine, like Mii chan, who love her, but I don’t know if she’s ever had someone her own age play games with her and be so kind. So this could be Rei stepping back in her mind and having a moment of disbelief, a little moment where she questions how this is happening and if she should trust it. And then of course she can trust it, because Ami is probably the most sincere person in the world (perhaps tied with Usagi).

On the other hand, I really like the idea of Rei having a little crush on Ami right back. I definitely read manga Rei as ace, and am ready to see Crystal Rei that way too, but there’s wiggle room for me on if she’s aro as well, so I could definitely see her blooming admiration for Ami leaning towards a romantic crush.

But on a third hand (can I have three hands? Just for this?) I almost think this is a flash of Silver Milenium memories. With the game being tied to Senshi fighting and Ami/Mercury being their strategist anyway, I think Rei could have had a moment of recollection from when Mars and Mercury had a moment just like this one, perhaps early in their lives when they were training or fighting low-grade monsters.