All plausible. May I add a fourth?
4. Lana appeals to Sofia's sensibilities, hearkening back to their conversation about her dissatisfaction with her marriage. Lana can cite that her marriage is not as perfect as her friends made it seem, and that's the reason she turned to Daniel. Sofia can then suggest that she, too, was seeking Daniel in order to alleviate some of the tension in her own marriage, and propose that they share Daniel. Now, either two things can happen: (1) Daniel can outright reject this, professing that his interests lie solely in his mother, or and I'd much prefer this (2) Lana outright rejects this ("jealous mode") and claims that because Daniel is her son, she cannot in good conscience allow him to have sex with one of her friends. Lana states that she's willing to face the consequences of her infidelity even it means having her trysts with Daniel exposed to Alex. Sofia, seeing how determined Lana is to protect Daniel, decides to respect Lana's decision and keep Lana and Daniel's secret to herself. Because, she--Sofia that is--actually is a good friend to Lana. As Sofia turns around and reaches for the door, Daniel reminds her that both he and his mother know of her infidelity, and that it would be in her best interest to keep quiet. Sofia pauses for a second, and then leaves. Just outside the door, she spots her husband who has been looking for her. Her husband asks her what she was doing near Daniel's guest bedroom, and she makes up an excuse to get them both away from proximity to where Daniel and Lana were having sex. Sofia reflects on the earlier events, alluding to how scary Daniel can be in defense of his own mother, and decides to give up on him for the foreseeable future.