If the employer is in one state (e.g., Maryland), but it has one remote employee working in another state (e.g., New York) who is laid off, do you apply Maryland's mini-Cobra or New York's mini-Cobra to that laid off worker?

I'm not a lawyer, so this is an uneducated guess.

Since it's (state) mini COBRA we are talking and not federal law, I believe it would fall under the residence. New York is more generous anyway, and if you apply the least generous, there could be issues, esp. if you base it on a state the employee does not even reside, could be problems.

Check with the admin or plan rules to make sure.

why don't you check your plan rules? The company must have a policy that coincides with the state law.