Complex sentence: The first woman that we see Chinaski meet in a bar, and who ends up being his most consistent companion throughout the film, is Jan (Lili Taylor), who, like Chinaski, is also an alcoholic.
Split into simpler sentences: The first woman whom Chinaski meets in a bar also becomes his most consistent companion throughout the film. This is Jan, played by Lili Taylor, who, like Chinaski, is also an alcoholic.