This is not a lawsuit. Their attorney made a demand to your insurance carrier for $18,000 for pain and suffering, wage loss, etc. This is completely standard in any auto accident where injuries are involved. Your insurance carrier will negotiate with their attorney to try and settle the claim. If your insurance company and the attorney do not come to an amicable agreement, they can potentially file a lawsuit against you. Your insurance carrier is responsible for representing you if a lawsuit is filed. They will either have in-house counsel or hire an attorney to handle litigation. You will not be responsible for paying these attorneys as your insurance company has a duty to represent you.