are there laws/guidelines for how long they
can delay payment?
Not really. And it wouldn't matter if there were. Depending on the way the policy was written and any complications like multiple beneficiaries, it could take a lot longer than 3 months.
Answer ALL of the following questions and I may be able to give you a better idea of what's going on and what to do.
First of all, who has or had the original of the annuity policy and where is it now?
Did the policy list more than one beneficiary?
Or did it list the estate as beneficiaries or no beneficiary at all?
Who is the executor/administrator of the estate?
What, exactly, has been sent to the annuity company and who sent it?