didnt like this one much

You are both very confused. This film is the one with which Almodovar reinvented the genre of melodrama. the crying is entirely intentional and well plotted. through manuela's crying we are moved... and not only through emotions, but also the plot. And also, by watching "habla con ella" it is obvious that Almodovar does not believe in coincidence but rather in fate and/or destiny, therefore, the job involving huma rojo plays a huge part. Manuela was offered the job with huma because of her loyalty and trustworthiness. as far as the story goes she is offered the job because of the homage to "All about eve" where a PA learns, or knows, the part of the lead and takes over. It is all a clever subtext and device to move the plot along.
She is also offered this job because all throughout the film, as the title conveys, she plays the mother of our characters: Esteban, Rosa, agrado, huma, nina, and even rosa's mother and lola. her motherhood and responsibility to others is her only vice. As far as the "redemption" she got from playing nina's part, there is none. she knows that part from before and had to play it again. however, what is important is her reaction to her childbirth. it is enacted with the same emotion as was when she lost her child. very moving. this is another parellel of the play and her life. as are as her three estebans, the father, the son, the holy spirit, and her sacred book, esteban's journal.
as far as lola goes, she may be the most monstruous character almodovar has created since Paul bazzo in KIKA and followed by Juan in LA MALA EDUCACION. i don't see any sympathy for her as far as humanity goes, but then again that is why she is stricken with AIDS. LOLA appears as the embodiment of death. only at rosa's funeral are we introduced to her and Manuela calls her an epidemic. Of course there is sympathy for lola but definitely not as much as is given to manuela. Lola is sympathized for because it is the nature of true christian love. a force that drives the films of almodovar. as rosa states: it is her duty to care for those, no matter how long she knows them, or what she does. a topic most notable in almodovar's films.

so as far as pash says, i answered the question: manuela becomes close because she is, at heart, a mother. this instinct is not something she can shake. she quickly grows bonds with many chracters in the film. not just rosa.
also, the part od manuela playing stella is answered above.
and whatever impromtu performance by lola you are taling about pash. it does not exist.

since neither of us have lived in barcelona (i've only been there once), it is not safe to judge the acts of those there. therefore, your analogy involving martians is highly ineffective.