What you wrote here sounds like it's about more than just financial issues an I am glad to hear you've raised these issues with your therapist.

I just wanted to add a couple of my thoughts about this:

1. Very important. Extremely important. She offered and agreed on a certain fee. That means (or it should mean) that she is okay with it. A therapist needs to take care of her/himself, rather than the client taking care of him/her. It's important in every way. Especially so the client won't feel obliged to take care of the therapist's unexpressed needs and try to read their mind (as it may have been the case in the family of origin for example) and so that the therapist will be modeling good self-care practice to the client. If your therapist is as good as you say, she has probably taken into consideration her needs and what you can afford. The fact that she's raised her regular fee twice in half a year also tells you she will ask for what she needs. So you don't need to worry, she knows what she's got to do.

2. If you really, really want not to write so much to her, you could do so without censoring yourself. Think of it this way: if you were in a face to face session, you might need to talk to her for two hours but the session may only last one hour, so you won't get to say everything you want in that one session, but that doesn't mean you haven't been open. You could possibly ask her what is an acceptable length of writing in her view and stick to that. One thing which could help (or at least it does in my case) would be to first write everything you wish you could say. That will allow you to express yourself as you feel. Then you could slowly combine sentences (for example if your thinking process while writing led you to a conclusion after 3 or 4 lines, you could write the conclusion more directly the second time). Cut back on anything that doesn't seem necessary. It can be difficult, I know. To me it's a good therapeutic process in itself and helps me to calm down if I do it in a particularly distressing moment. I do this when I text my therapist because he has an old phone which can only receive very short messages. It actually helps me to clear my head and realize what's most important to me.