The seller's agent cannot sue you--she is not a party to the contract. The seller can potentially sue you if you do not close. If the seller does, you could try raising fraud as a defense since fraud would let you void the contract; you could also bring a counterclaim for any costs or losses you incurred due to the fraud. However, bear in mind that fraud requires knowledge: it is only fraud if you can show that the seller knew about issues but despite knowing of them, failed to disclose them. It is not fraud if they did not know, since you do nothing wrong to not disclose something you are yourself unaware of. So you would need to be able to show that the seller knew, or under the circumstances logically must have known, of these issues.