Employer is not providing releaving letter, experience letter

I and my wife are working in Kolkata, West Bengal. My wife is facing some issues with her last employer which I am trying to explain as much as possible: My wife has been working in her last (Payroll) company since July-2017. She left her last company on 15-Dec-17 without serving any notice period. She tendered her resignation via email to her payroll company on 14-Dec-17 due to mental harassment and unprofessional environment at work place. She also agreed to pay any applicable amount in lieu of Notice Period of 2 months (PILON) as mentioned in the "terms and conditions" of her appointment letter. She also explained her situation regarding the issues she has been facing at workplace, when her employer responded back to the resignation email but even after that no action has been taken to address her concerns regarding workplace. After that, HR keeps forcing her to serve 2 months notice period which she was not comfortable with. At multiple occasions, HR threatened her that they would tag my wife as "Absconding". After repeated request to settle this issue by paying any applicable amount in lieu of Notice Period, HR did not show any interest to resolve to issue in a professional and peaceful manner. At last, employer send her an email that her employment is terminated on a disciplinary ground as she did not serve any notice period and they would not provide her any releaving/experience letter, pay slips, character certificate etc which are important documents for next job opportunity. The employer also held my wife's salary for the period worked between 01-DEC-2017 till 14-DEC-2017 which showing any cause. Now, she is facing difficulty finding any decent job in any good company as all these companies are asking for experience letter and Pay Slips (last 3 months) from Last company. After the termination email, my wife did send another email raising some questions regarding "termination letter" as she has already resigned, and also notifying them that she will take legal course of action if the employer does not provide her with these documents along with any due salary and final settlements. Now, we want to know if there is any hope for us legally and if yes, then what legal course we should take to address our concern?