Rosalind

Corin Ashby's cousin, visiting Solmere as a guest entry in the Sports Festival.

Before she appears

Ch. 285. Finn's betting sheet has Briar down as "unlikely" in the academic relay, and the reason is her:

FNN: Corin's cousin, apparently. Visiting relative, competing as a guest entry. Word is she's exceptional at rapid retrieval tasks.

What she is like

The opposite of her cousin, immediately.

the young woman beside him offered a warm, easy smile that carried none of Corin's usual careful reserve.

ROS: You must be the group he's been writing about. It's lovely to finally put faces to names.

Then she exposes him without hesitation.

ELS: He's been writing about us? ROS: Extensively, actually. Though I'll admit he'd deny it if pressed.

ROS: He described Elsie as, and I'm quoting directly, formidable in ways that continue to surprise him.

ROS: And Arthur as someone whose rivalry he considers, again quoting, the most genuinely interesting development of his entire academic career so far.

Corin's response is the only one available to him:

COR: I regret inviting you. ROS: No you don't. COR: No. I suppose I don't.

This is the first outside confirmation of what Corin actually thinks, and it comes from letters he wrote home, which is where the saga has been putting his honesty since ch. 276.