Sorry if spoilers aren't supposed to be here, but no other way to describe the bug. At the end of the Vault 114 mission to rescue Valentine, every time Darla runs away (peaceful dialog options) the game crashes. The one time I tried a hostile dialog ending (not my preference) the game did not crash immediately.... but I died pretty quickly (since I normally DO choose the non-violent paths) so I am not sure if I would eventually crash or if that's the only way I can advance this quest.

I did not use any cheats to get into Vault 114 (as I have heard some people have problems using TCL to enter the Vault, etc). Everything was normal up until Darla runs.

I've got a handful of texture mods and a few settlement mods and such but nothing that (I would think) should be affected by Darla getting a peaceful ending and running away.

EDIT: I finally just coaxed Darla into attacking Skinny --- not as peaceful as I would have liked, but at least the "innocent" girl survived, and I was able to advance the mission.