Well there's a lot of things we don't really know, but it's not difficult to imagine a secret agent could find his pregnancy-weakened twin sister he's spent his entire life with. We don't have a reason to think she went anywhere other than back to the tribe.

Raven was pissed about Summer replacing her

We know Qrow confirmed she wasn't coming back, albeit with the possibility that it was after Summer's death. But she can be mad about getting replaced all she wants, you don't get to decide your ex's life after you ditch them.

The short version is, I think the default story with a minimum of drama and backstabbing makes the most sense and is easily the most likely. You almost have to go out of your way to find a scummy interpretation, given what we do know.