I generally agree with the others. In theory you can have two personal representatives, but that seemingly will not help you with the core of this issue. The key is to open the lines of communication the best you can, and as a last resort, involve the probate court.
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Putting aside any owed salary or accrued vacation time, and also assuming no grounds for racial or sexual discrimination or the like, the terms of employment itself are usually changeable at will by an employer, written offer or not, unless the contract / offer letter makes specific guarantees as to employment term and termination.
Agreed that the short answer is no, with limited exceptions that have mostly already been cited by others. Power of attorney cannot be used for a deceased person. Your best bet is to see an attorney. If she has a truly small estate (under $25k and no real estate) and no one will dispute you as administrator, you will have some relatively inexpensive options for probate, and the cost can be reimbursed to you from the assets she does have.
When you say he owes you $200 was it for renting the room? If so, or if he paid you under a separate arrangement to use the room, he might be a tenant whether or not a lease existed. If no rent ever changed hands then I would still do the certified letter thing. You should make the best case you can that the stuff was abandoned before you throw away or sell it.