If you go to where Zevlor is standing here in the grove there is an exit to the left up some rocks. When you go out this exit Karlach's spawn point is a jump down the cliff on the right. You'll take like 90% damage if you don't have featherfall or something similar like misty step but you get to her super early and don't have to deal with any other combat.
I'll do anything to get to my favorite companion early.
Video link demonstrating the route to her:
I've been doing the Grove battle, then heading straight west across the bridge. Once I get to the Blighted Village entrance, head north, grab Scratch then jump across the rocks at the river. Then head east and meet up with her.
It is the same path as above ? I remember during early access fighting ton of mobs before reaching her. So i'm glad there is a shortcut and she was very cute during the last panel of hell, straight forward and honest. :)
As long as you don't stray off that path or enter the Blighted Village you will not run into any enemies.