娘: a daughter or a lost young woman
Compare a daughter who will begin living alone in spring with a young woman guided to the station. Read the relationship in context, keeping the future move separate from the completed guidance.
A daughter's future living arrangement
娘 (むすめ) can mean daughter. “娘は春から一人で暮らし始める。” (“My daughter will begin living alone in spring.”) describes the speaker's daughter beginning to live alone in spring. 春から supplies the starting point for that change.
The move belongs to the future in this scene. Keep that timing with 暮らし始める rather than reporting that the daughter has already started living alone.
The young woman in 娘さん
In “道に迷った娘さんを駅まで案内した。” (“I guided the lost young woman to the station.”), 娘さん refers to a young woman who had lost her way. The speaker guided her to the station; the example does not identify her as the speaker's daughter.
道に迷った describes her situation, and 駅まで gives the destination of the guidance. 案内した reports a completed action, rather than a plan to guide her later.
Read the relationship beyond さん
さん alone does not establish a daughter relationship. The scenes identify a daughter with a future change in living arrangements and a young woman who needed directions.
Keep the people and timing of the two examples separate. The daughter will start living alone in spring, while the lost young woman was guided to the station. The shared word 娘 does not make them the same person.
Does guiding 道に迷った娘さん to the station prove that she was the guide's daughter?
Show the answer and why
No. 娘さん refers to the lost young woman in this example. The presence of さん alone does not establish a family relationship with the person who guided her.