She's the boss, so part of her responsibility is to keep in touch with the office when she is gone, which isn't really hard these days with internet, smart phones etc. If she is really busy/grieving etc. then she has the option to not check e-mail or not respond, but as an employee, I would let her make that call, not me.
Get used to me. Black, confident, cocky; my name, not yours; my religion, not yours; my goals, my own; get used to me. -Muhammad Ali