Use the Memory Reader

You take the Charlotte's head. You tear a hole in the back of her neck and push your head through it. It takes you some time but you managed to put on Charlotte's head.

Then you turn towards your bed, where the Memory Reader lies. You stand up, businesswoman's skin hanging loose from your neck. You step towards the bed, take the reader and immediately use it by pressing it to your head and pushing the button.

Charlotte's memories flood in. College days, parties, early business days, countless clients, etc. Still, you try to ignore the majority of memories, to figure out why Charlotte was inside Anna.

Aaaaand........ There it is.