This achievement is very easy, just enter Marie her room.
This is the second / middle door; the one with the poster on it.
As soon as you open the door, the achievement will pop.
If you are going for the "
The Complete Picture" achievement
, then do not forget to interact with the following items in the hallway:
*** Spoiler - click to reveal **** Try interacting with the stairs
* look at the picture on the wall
* look at the first door (bathroom)
* look at the wine guide on the table
* look at the picture on the side table
* look at the third door (also nothing on the door) to the parent's room
* look at the weather station
* and now open the door to Marie her room