My question involves an injury that occurred in the state of: FL

Hello, and thank you for reading and taking the time to share your opinion.
I'll try to keep it short, but if there are details that could help let me know.

Status of my vehicle:

I had been sharing an auto policy with my grandmother for many years while I took care of her needs. She was in her 90s and not self sufficient.
She had a vehicle that she let me use whenever I needed it, which happened to be a long time for reasons that are not relevant.
Last year my grandmother passed away. My father lives in TX and my Uncle lives in NY(her only 2 children).
My father had POA.
I tried to get the title transferred into my name but the tax collectors office said my father needs to be present. Once again he lives in TX.
At this point I just added the car to a new auto policy in my own name. The title is still in my grandmother's name.

Nature of the Accident:

I was involved in a 3 party accident. Party 1 was stopped on the interstate (far right lane). Party 2 saw them late and rear ended Party 1 on the left side. Party 3 (Me) tried to avoid the collision by maneuvering to the right shoulder. Right shoulder is under construction with concrete barrier with not enough room for the entire car. My left mirror and door side-swiped Party 1's rear/right quarter.

Party 1 (4 people) got out of the car and we hung out and talked--even laughed with me. No one was injured.
I was not issued a ticket.
All vehicles were able to move under their own power.

Current situation and Question

Later, two of the people from Party 1 claimed Injury against my policy.
They are now demanding an Affidavit from me as well as my deceased grandmother, as the car is in her name.
In FL I am not required to complete the affidavit.

I did not inherit anything from my grandmother, and I do not know of any estate left in her name.
My financial situation: Solid, I think, for a 27 year old. I own 2 cars (nothing fancy, combined value maybe $8,000) and have a house on mortgage. I have a pretty middle class salary. No kids, not married. Saving for retirement in several types of accounts.

Should I disclose to my insurance company that my grandmother is deceased and therefor cannot sign an affidavit? Or will that bring me more trouble?
Should I sign the affidavit? I feel like the answer is no...

If I say nothing and don't submit an affidavit, is it likely that they have grounds to take me to court?
I don't know what to do and hope someone is patient enough to read all of this.

In my opinion, Party 1 is just aggressively trying to demand everything and just see what comes up. Like I mentioned, there was no injury at the scene, and the damage actually caused by my sideswipe was minor.
Party 2 was primarily at fault and I believe was ticketed, however I believe this party to have state minimum insurance limits and little to no assets--therefore coming after me instead.

Sorry, that was not short.