• Seeking divorce and maintenance from non-supportive husband

My Sister is Married since 2007 at at age of 35  Before Marriage she was employed as a government school teacher. Her Husband, my brother-in-law who was then 42, is employed with a Leading Airways in a senior management position. Based on her family her Job profile, we accepted the alliance and soon after marriage within a month shifted to Mumbai. She also took a sabbatical for a year from her Job,  and was planning to resign after a year. This was more of an insurance in case things don;t work as desired.
Soon after reaching Mumbai, she realized, her newly found husband is carefree and self centered without any savings, living in a rented apartment and a huge liability. Her husband was not considerate about her and she found her self all alone without much support from him.
In the mean time, she conceived but things didn't turn up better so after staying there for about 8 months with about 6 months pregnancy she decided to conceive at her paternal place, Kolkata. She flew back all by herself, and rejoined her Job. As an unfortunate turn of event, there was a delivery complication, and the baby was in NICU for more than a month. Even after that doctors advised to continue to stay in Kolkata. In the mean time, after staying 2 months with her in-laws she shifted to her parents place and continued to stay there. She requested her husband to help her financially, but he was not cooperative. Within a year and a half, it was soon evident that the baby boy was autistic. Even after all efforts travelling to different places including NIMHANS there were little improvement.
There were still no support for her husband and used to irregularly wire her just 10,000 bucks for supporting his Kid though his net salary was closed to 90K/month. She was skeptical to fly back to Mumbai as staying with him for 8 months it was clear that he would not be able to support her and the Kid. Moreover without any physical, emotional and psychological support from him, she best decided to continue to stay in Kolkata with her husband occasionally visiting her. 
In the mean time with her savings and with my support she purchased an apartment with rest of the finance from Bank, the entire EMI being supported from her salary. She initially though that she can somehow change her husband's mindset by making him more accountable so added him as a co-buyer in the apartment. In the mean time she conceived again, and fortunately it was a normal delivery. 
But even after that her husband was not a bit supportive and even stopped sending money regularly. Things turned bitter and she is now least hopeful about the relationship.
Now currently she is supporting her two kids, her Job her EMI all by herself, and our parents who are getting old is staying with her. She is now seriously contemplating for separation and ask for regular maintenance from her husband. 
Unfortunately at the current scenario, she is not in a good financial position to hire a good lawyer nor she knows any one out there and feels helpless as to how she should proceed.
Can you please help her realize what is the best way she can proceed now?