It is an interesting glimpse into Josy's mind. While this is a great opportunity to make a new friend, she does seem to ignore the obvious downside of paying so little attention to Maya right after they finally had a chance to reconnect. I think it comes down to taking a certain rapport with Maya for granted.
From what we can tell, Josy and Maya were friends for years before they finally became lovers, so they probably can legitimately count on the other understanding why they behave the way they do in a given situation. As Maya says, Josy is always making friends; she knows that about Josy and likes it. So Josy probably assumes Maya would understand why Josy changed her plans, secure in the knowledge that Josy and Maya will have other chances to spend time together (on topics more fun than the campus map).
And on a surface layer, Josy's no doubt correct; I very much doubt Maya will hold even the slightest grudge over this. But I do think it illustrates how Josy didn't quite realize just how fragile her relationship with Maya was. Sure, she and Maya will spend time together soon enough, but each of them is clearly very bothered by how the other handled the isolation over the summer. It's telling that they never got around to learning each other's history with the MC until the big ruined library scene at the climax of the episode.
We can see something similar happen in Episode 7. Josy correctly predicts Maya's reaction to Josy joining the HOTs; she also knows that even if Maya understands the necessity, she can't help but be a little resentful. Yet Josy still seems to assume she and Maya will be able to iron it out without it taking any extraordinary actions on either's part. I found it very odd, for example, that when Josy asks to spend the night with the MC, the idea of inviting Maya too was never considered. It's certainly possible Maya doesn't want to leave her dorm for fear of a surprise inspection, or that the MC/Josy is worried about making her feel awkward, or even about the logistics of smuggling two girls into his room instead of one. But it's still a very remarkable omission.
As I recall, the idea that a relationship is a complex, evolving thing that takes constant effort to maintain was one of the major themes of
Acting Lessons. So it would not surprise me if that theme will reappear here with Maya and Josy. Then again, it could be this was just a simple way to show Josy was still angry at Maya and see her becoming friends with Jill in one move and I'm way overthinking things. Hard to say for sure.
