If a girl says next time I do it for you, I never return. It is one of the oldest cliches in the book in this industry, along with only for you, you are so big, so handsome, come so much, I come so much etc etc.
If she doesn't want to do whatever now, then that is her decision to take the chance that there will be a next session. And I am a low mileage guy in general, so take it for what it is worth.