First you need complete the Main quest
Hunting a Witch in Velen, while on you find Keira Metz. With her you complete the Main Quest
Wandering in the Dark and then ask to do the Sidequest
Magic Lamp for her. Complete it to get the Sidequest
An Invitation from Keira MetzThen there are tree Sidequests (
A Towerful of Mice,
A Favor for a Friend and
Advancement of Learning) that you need to complete. If you have a Conversion with Keira you don't to need to be nice to her
but don' t use the leave Conversion option with the X, if you do that the Quest will fail! For the last Quest
Advancement of Learning: Here you can kill her or walk away (Quit conversion Icon), you get the Achievement after.
If you kill her the Full Crew Achievement will be not unlockable!