I'd argue that OP likely knowingly permitted the guest to go smoke on the back porch. It follows logically that OP knowingly permitted the guest to extinguish the cigarette. Did OP provide a proper receptacle for that purpose? The fact that OP doesn't smoke suggests the answer may be 'no'. Did OP follow up on or supervise the activities he permitted the guest to perform in the rental unit he had agreed to be responsible for? The fact that the dwelling burnt down suggests the answer may be 'no'.
An insurance company is on the hook for $200k here. OP needs a lawyer before he attends this 'meeting', which may progress to a deposition soon.
A tenant is not strictly liable for the actions of their guests, negligent or intentional, as a matter of law. There may very well be a duty based on contract under the lease. There there might be a duty of adequate supervision. Even under contract, the tenant is not a guarantor of all the guest does.
Since a cigarette can be extinguished adequately and completely using many methods, there is no legal duty to provide a "proper receptacle" in a private residence. The knowing requirement would need the tenant to actually see the guest put out the cigarette in the plant pot or tell him to do so. Grown ups do not have a legal duty under the law to supervise or follow up on the normal behavior of their guests. There MAY be such a duty under contract. There, the specific facts would need to be known.
It is a logical fallacy to argue the premise from the antecedent. This one is called affirming the consequent.
1. If A then B.
2. B
3. Therefore A
That is an example of a formal or deductive fallacy. The only place such things have in law have to do with res ipsa loquiter which is not implicated here. Even with that legal theory, there are other elements required that would indicate B has no other possibilities of happening but for the negligence of the person who is in complete control of events.
I think anytime any serious person like an insurance company or lawyer is even mentioning the fact one might owe them a couple hundred thousand dollars, it is well worth the time and money to see an attorney. Only through an attorney would one want to talk with the insurance company. It would be very easy to admit things that should not be admitted in a conversation. Using a "mouthpiece" could not be used against the OP in the same way.