In my experience, emailing between sessions is not a problem for everyone. It does seem that some people don't do well with managing it. I don't think it's helpful to have a one size fits all approach just because some people have a problem with it. In my case, I have needed less between session contact over time and been able to reduce sessions, so it's not always the case that it increases dependency.

OP, it may be that your therapist isn't bringing it up because a) you've had other things you've wanted to discuss and she follows your lead or b) she feels it's more helpful if you initiate the discussion.