Landlord deducting advance raising terms not mentioned in agreement

Hi, I rented a house at Bangalore around 7 months back. Now I have to move out of the area as I have to change the job. I gave 2 months notice to landlord as per our rent agreement. Now she is telling I should stay for 11 months minimum, else she will deduct a month rent from the advance. This was not mentioned in agreement. In agreement, it specifically mentions I can leave by giving 2 months notice. Agreement validity is 11 months. But no where it mentioned about minimum duration of stay and related penalty. Please let me know how to proceed in this case. Should I challenge this now itself, or after I secure what ever advance they are willing to give. I have proofs of the conversation as it happened in Whatsapp.