Resident passing away; can assistant living apartment be rented to new resident?

My mother in law just recently passed away On April 17 at an assisted living center. Because we did not give 30 days notice that she would be leaving her apartment, we will be responsible for her apartment rental until May 17. Does anyone know if this apartment can be rented to a new resident before May 17 or is it considered hers until then? If they do rent it out before May 17, is that considered legal?