Seeking divorce from her is the problem he can think about.
He cannot mention the relationship between you and him as a reason for seeking divorce from her.
He has to look for some grounds viz., cruelty, non-cohabitation, willful refusal to have conjugal relationship etc.
In any case she cannot make any complaint against you for having an extra marital relationship with her husband.
As per law a woman is not entitled to file an adultery case against her husband too.
Her complaint against you for having extra marital relationship with her husband will not be entertained either by the police or the court because there is no provision in law for that.
If you have married him during the subsistence of his earlier marriage and she proves the same beyond doubt with documentary evidences then you and your paramour are liable to be prosecuted under bigamy laws.