Continuity mistake: When Alex throws the useless GDR money from the rooftop Lara is sitting on the rim, wearing a red t-shirt. When Alex walks over to her and she gets up she's wearing the light-blue jacket she was sitting on. (01:07:35)
Continuity mistake: At the datscha the mother tells her kids how she lied to them about their father after he had left. She is rested on a reclining chair with a brown pillow. A second brown pillow appears and disappears in alternating shots. (01:29:40)
Answer: Lara did indeed tell Alex's mother the truth. Realizing how much her son had done for her, she left him with the illusion that she never found out. The audience knows better.
Ioreth