Oh, I'm so sorry your therapist has cancer.

My therapist has cancer too. We have to schedule around his chemo treatments, but otherwise he is mostly okay. So my situation is really rather different from yours.

I don't know what I'd do if his cancer takes a turn for the worse (it could although I'm hopeful that it won't). These feelings are really hard--wanting to help but not being able to, feeling like your problems are trivial compared to cancer. I've experienced all of those feelings, and they are totally normal.

What I would recommend is for you to talk to your therapist about various worse case scenarios. If chemo makes her really sick and she's unable to work, is there a colleague you could contact to get updates about her status or get reassurances that she is okay and just needs time to recover? If she is unable to work for a long time, is there a substitute therapist you can see temporarily to help you through this rough time? It might help if the temp therapist is a colleague/friend of hers so you can get information/updates through that person.

And the very worst case scenario, if she dies, what happens to you? How would you find out? Will you be allowed to go to her funeral (if you want to go to her funeral)?
What will happen to your file? Has she designated someone to take over her practice if she dies? If not, can she provide you with some referrals (if you want referrals)?

These are very difficult conversations to have. And I must admit that I haven't had them with my therapist because he's assured me repeatedly that he's fine and does not expect to die any time soon. If he starts to get more sick, I will have these conversations with him. (But he actually appears to be getting better so I'm not super worried right now.)

I should probably at least have the "how will I find out if you died" conversation with him anyway because I've read so many horror stories. If I have to find out about his death through an obituary in the newspaper or a note on his office door, I will probably lose it.