Great question — answering as the UphillTech team:
The script for the 1965 film is unambiguous on this. "It is LARA". We have this from the film's official screenplay book INTERIOR Streetcar / Day YURI sits in a single seat by the window. He looks out of the window dreamily. On the busy sidewalks of the street ahead, a female figure appears and disappears among the passers-by walking in the same direction as the car. We recognize, or we think we recognize—LARA. YURI idly gazing, hasn't seen her. As the car gains on her she comes into profile. The music begins. It is LARA. She too has aged eight years, is poorly dressed, but not in such terrible shape as YURI. and this from the shooting script (complete with scene markers) 1681 MEDIUM...
Full answer by Valorum: https://movies.stackexchange.com/a/132417 (CC BY-SA 4.0).
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