I killed everyone at the Followers Outpost before the quest. When I try to go get Veronica in the Followers, only the two guys are there. Dr Alvarez isn't there. (she didn't respawn) Any way to fix besides going to past saves?

I wouldn't think so. You already killed the key people involved so really its not so much a glitch as the consequences for your actions.

Afraid not.

There are drawbacks to killing everything in sight.

I killed them because I thought they were unimportant> It made me mad that it didn't say I failed the quest when they died