While my therapist hasn't done the same things, she works hard with long hours, yet does even more work outside direct client work.
I too have had concerns because of stuff I know about her over the course of our therapy. Plus I've worked really long hours myself out of a sense of responsibility in a demanding field and have burned out twice.
I decided to be relatively blunt about my concerns after prefacing I know it isn't my role to take care of her.
I asked some brief yes/no questions about her supports -- with the disclaimer she can of course not answer.
I explained my thinking, then asked how could I show care since I obviously aren't a friend etc -- she knows I'm huge on showing care and appreciation to friends, and I correctly pinged she has some tendencies towards self sacrifice. She told me the best thing I could do is to take care of myself the best that I can.
Recently, I chanced upon a short interview she did (she's quite well known in my local area, I wasn't hunting for anything) where she had mentioned working long hours out of a deep sense of compassion, although that ups the risk for burnout. She was also explicitly thanked in the interview for using her personal time in her already busy schedule to run some rather time intensive things.
So I saw her for therapy and as we were wrapping up, I briefly referenced the interview and remarked she hasn't seemed to take a break for quite a long while as we've an agreement she'd try to give me some advance notice for breaks. She then told me when her next break would be and how she hopes she'll take the break rather not.
Before my burnout, she would encourage me to take a day off work or even a week off, but it was really difficult for several reasons due to the nature of the job. So yeah, I cheekily quipped she better get that break and rein in her self sacrifice schema.