Go with what works!

Possibly, you could compliment the boss on her hard work, and ask about her vacations, and suggest other great vacation spots. Tell her that in her type of job, stress is inevitable, and many people need frequent get-aways. (Anonymous travel and vacation brochures could be placed in conspicuous places that the boss is sure to see.) A win-win situation. Good luck!

PS: I had a boss like that once; now I’m self-employed.