Question is it possible to get both Meridyx and Olivia at the same time and if it is how???
Side with Olivia during the Knot Cave quest. Choose not to kill Meridyx after fighting the Warlock (I forget his name)
Offer a place at the Wayfort to Olivia
Complete Knot Cave (no gender-bending the lupine, Olivia does not approve)
Upgrade the Wayfort (If you haven't already)
Olivia arrives.
Travel around Old Forest after completing Knot Cave - Meridyx will become a random encounter.
(I can't confirm the method to recruit Meridyx - as I haven't encountered her enough times)
But so long as you don't side with the Warlock or Kill Meridyx - than you can get both.