Yes, I would have a chat with your trainer and ask about her expectations as well as lay out your own concerns- what homework should you do between lessons, should you be warmed up before the lesson, and are there days when you can focus on flatwork more, if that is what you want.
Going slow is fine unless it means you are treading water, so unless your mare was seriously labored at the end, perhaps you need to update your expectations of what she is ready to do, too.
I grew up in H/J world and by the time I was doing the Juniors, I would have half hour jumping lessons because there was nothing much to work with me on the flat at that point. Our hunters knew basic dressage, and even though I had green horses I was capable by that point of bringing their flatwork along myself, including doing equitation stuff (counter canter, turn on forehand), as well as hacking out on the hills to keep them fit. The jumpers in the barn, however, got much more focus on flatwork because they needed it more.
My current trainer is an eventer and under him my dressage abilities have grown exponentially- he is a stickler for really correct work, and knowing exactly where your horse’s feet are every step. Even those days where we mostly jump he warms me up with pretty intense stuff- lots of lateral work at the walk and trot, then things like: canter, halt, turn on the haunches into canter again, with maybe a pirouette thrown in, into medium canter, then canter in place, etc. Some days we mostly flat- some days I go up there ONLY to flat, so we can really work on whatever it is that my box truck of a horse needs that session.
I LOVE this method of teaching, but part of why it works is that we each have clear expectations of the lesson and my end goals. So, to round this out- definitely follow through on your plan to talk to your trainer and make sure you are on the same page. 
