A: So, no party tonight?
B: No, there is a lot of discussion.
Is B saying there is no party?
A: So, no party tonight?
B: No, there is a lot of discussion.
Is B saying there is no party?
You are correct. B is affirming that there is no, or will be no party.
The additional information about the discussion implies that it was about the party and whether or not to have it. You can speculate on the nature of the discussion but the outcome is no party. Perhaps another time.