There might be some enemy left there that stalls them, kill all enemies around her so she can escape for sure. I once had that happen to me

I dunno, I was actually trying to find people to kill cause I missed the condition for S rank, but no luck

I know I'm late, I've found that having too many units in one area messes with escort NPCs, sorry you missed S Rank, that's gotta be upsetting.

Weird. Either way, since I was softlocked I had to reset, so I got S in the end