Also, if the CO office doesn’t work out for the startup, they may ask her to come back to SF. At that point, the door would be closed with the established local office, and maybe others in the area, because of reneging on offer. Unless she really doesn’t feel excited about the new company, it sounds to me wiser to move to it now, rather than take the chance that the startup plan (which seems totally based on her actions, not something that had been in the works) doesn’t pan out