The West Wing is part of Croft Manor in the Blood Ties DLC first published with the Rise of the Tomb Raider: 20 Year Celebration edition. Like all the rest of the manor, the west wing has suffered heavy damage and is in need of repairs; e.g. there is a tree that has crashed into the windows of the corridor leading to the Master Bedroom and the Atelier.
"I'm sorry, I just wanted to see –"
"We've been through this."
"Was... mom's room in here?"
"Just stay out of there, darling."
During Blood Ties, Lara comes here in the search clues leading her to the combination of her father's safe.