My other track of thought tells me she might be bored at with her current room at DC...
Definitely possible.

I have seen this before in kids who have been TTd for ages, then they revert, but it seems really odd, because it never happens at home, and hasn't happened for ages.

In one case, the child was just getting exhausted at CC, really running herself ragged, and then (we postulated) falling into a deeper sleep, so not really waking up with the need to go. But she was much earlier in her toileting career.

In another case, it was in a room where children played on their beds if they didn't sleep, until a particular time (2 o'clock) But if you wet your bed, it got packed away, and then you could go and play anywhere in the room (again, just theory) So boredom was a major cause.

Have you pointed out to CC that it only happens in one particular room? That might help them to come up with some strategies.

If it's not happening at home, I'd say it's not a lot to do with the new little guy, unless all the CC workers are constantly asking about him and she's over it. I've seen this happen too, CC people do tend to love babies, and get so obsessed with new ones that they forget that the child in their care maybe wants to talk about/do something else or be their own person.