No, you cannot live together in a live in relationship or get married until and unless the husband and wife divorce each other and get a divorce decree from a competent Court.
You should know that it would be a crime if a married woman live with another man in a live-in relationship and such man will be considered a criminal under Section 494/495 of Indian Penal Code and will be liable to be punished.
There will be no acceptance of your relationship even legally.
So, you both should solve the issue mutually and discuss it with the husband of the girl and then they both should get divorce.
I would also suggest you that for more clearance, please consult a lawyer.
I hope I was able to help.