In the US, at least, parents of minors do have most of the rights when their children or teens are in therapy. I think that the most important thing for the parents to consider is not what rights they have as parents, though. What should be most important is what is really best for the child. It is reasonable to ask your daughter and/or the therapist if progress is satisfactory, and certainly ask them what you can do to best support the goals of therapy. I think joint sessions are great most of the time, if your daughter agrees to including you in a session or a few. If you think that therapy may be going on too long, or if it is starting to strain the budget, you could talk to the therapist and to your daughter openly about your concerns. I hope that you would be sensitive to your daughter's and the therapist's responses. Even though you have seen progress, there may still be something that they are working on. Keep in mind that everyone who establishes a good connection with their therapist, adults and teens alike, will have strong feelings for that person and ending the relationship can be the hardest part. If it is too abrupt, it can be a traumatic loss. So, if you have reason to, you can suggest that they start moving towards wrapping it up, but please do consider what your daughter says about that, and let her have some time if she needs it.

It's a frustrating position for a parent to be in, because you might feel shut out of a significant relationship in your child's life, and all you have to show for it is the bill. Think of it as a gift that you are giving to your daughter, that will help her now and throughout her life. If there were serious concerns about your daughter's safety, the therapist would be obligated to tell you, and it sounds like there are not and you don't suspect anything seriously wrong. That is good. You might need to be satisfied with that. You could push for more, but it would come at the cost of undermining your daughter's trust in you, and maybe destroying some of the progress that she has made.