Hmmm... Haven't even thought of that.
I'd imagine it was difficult for Charlie to win her trust.
Like, I could see Vaggie just wanting to get out of Hell immediately, and walking up to the Exterminators, thinking they'll be able to do something about it...
Only to loose an eye from the spear.
Cue Charlie, engulfed by demonic rage, attacking and chasing the Exterminator away, and terrifying Vaggie even more in the process. It took a lot of care and nurturing from Charlie to get her out of her shell.