She can file a case under section 13 Hindu Marriage act on ground of adultery and can claim maintenance, alimony from you. She can also file cases under Domestic Violence and other such provision.
I would advise you if she has proof of your extra marital affair and she is in agreement of filing for a mutual divorce you should agree to it bargain on settlement amount. Because contested court cases takes time she has valid ground and you have to suffer a lot in unnecessary litigation. So best way is to get mutual divorce and start your life again.