Cosima, whenever she is vulnerable or angry, has a tendency to put physical distance between herself and Delphine. While this isn’t unusual for anyone, the lengths that she goes to do so are. She keeps Delphine much farther than at arm’s length, more often than not with some physical barrier between the two of them, because without that, she knows her resolve will break. She uses the desk first, then the table in their laboratory, as well as the door to (again) their laboratory.
If physical distance isn’t an option, as Delphine often breaks through that space, she immediately goes on offense verbally, most notably with the “Yeah, it showed.” On top of that, if Delphine tries to breach the physical space between them, and Cosima’s resolve is in fact cracking, she sends her away - first in her apartment, when she finds out Delphine is working for Leekie, and again, after she finds out about Kira’s stem cells. (“Get out!” anyone?)
More than that, in the moments when Delphine does manage to get through, such as the scene in Felix’s loft, when she reaches for her and Cosima pulls away, but later accepts the gentle prod in her lower back, we see her defenses fall hard, and fast. Not long after that moment is when she admits she’s sick.
Cosima cannot hold onto her frustration or anger when physically near Delphine. It’s been obvious from the beginning. Inevitably, she gives in, which is why she puts up so many different defenses, both physically and verbally.
(screencap credit x)