Her husband is playing the long game and taking his sweet time by not letting her out of the marriage. If she did end up marrying you, it would have been bigamy which is a criminal offense with possible punishment for upto 7 years. Section 494 of IPC.
My advice, put it in writing you cannot and will not proceed in any relationship with her and it was she who approached you. Otherwise thereโs nothing stopping her from filing false cases on you too. Trust me this is becoming more common in India these days.