I can relate to the feeling that you're being "mean" to your therapist. After my uni therapist said "I love you" I actually lost my s h i t. I became really depressed, tried to quit, and then I got angry. I've been horrible to her. I accused her of lying to me, and generally just behaved like a total twat. I had an absolutely insane reaction to it. I couldn't digest it, and I feel really ashamed of it now but at the time I could not control my emotions.

I think the same is true for you, with your therapist going on maternity leave. You're having a reaction to it, and sometimes we can't control that. The feelings are too intense, and they just have to come out somehow. You need time to digest. Don't feel bad about that.