There's something about how Eva mirrors Grace's behaviour, gestures, expressions, and words from the very beginning that is fascinating to watch.
I read both of them as autistic, so I see the mirroring as both something that happens unconsciously and consciously, to a degree.
Generally, autistic people tend to have a harder time with social interactions for many reasons, including the lack of mirrored behaviour. The vast majority of the time, it's just something people do, it helps us connect to each other, it can express sympathy and "I like being around you", it solidifies relationships.
When you're autistic, that often does not come natural. We run on different software, our social behaviour, the cues we read and instinctively respond to, are so different from allistic people it's a real barrier. It's one of the reasons we're often perceived as rude or aloof.
Considering Eva's role, she is a) aware of herself and her behaviour and b) doesn't always bother to mask. She doesn't have to, it's GOOD that people do not like her, she is not meant to be liked.
She's read his papers, she knows who he is and who he was, she knows what he struggles with and what she needs to do to get him on board (different post entirely but also an interesting one).
Eva responds to him, when he makes a facial expression, she does it back. When he uses a specific word or phrase, she says it back to him. She positions her entire body to mirror his, she moves, talks, breathes like there's a literal living connection between them.
It's validating for him, to have someone who is interested in his research, his thoughts, opinions, actions — all of it. Someone who thinks he is important, that he's right, fuck everyone else.
It's why they orbit each other in that specific exclusive way that has everyone else thinking they're hooking up, it's an infinite feedback loop until the very end.
