That would bother me too. My T is often a few minutes late but we usually go late, or sometimes he’ll end early and it bothers me but I don’t say anything because we do go late sometimes, and he allows contact between sessions at no charge so I still feel like I’m getting my hours worth.

I do think it’s important to bring up, so maybe something along the lines of “I noticed we usually start late but always end on time. Is there something I can do to ensure we always start on time so I get my full 50 minutes?” I would put it on me and not say “you’re always late” (even tho that’s actually the case). Hopefully something like that will get her thinking about how her punctuality affects her clients.