My grandson wasn't talking when he was 2 1/2. His pediatrician referred him to both a private speech therapist and the school district. Federal law mandates that they make evaluations and provide treatment if needed. You definately should not wait until she is 5. They told my grandson's mother that if she'd brought him in sooner he could have more help at home. At three he started in a preschool paid for by the state. He was not improving speech wise and was acting out. Again the school district provided a therapeutic preschool and his behavior has improved immensely. At 4, he is still struggling with speech and they are going to place him with a therapist who can see him every day.
Your daughter is obviously much better at speech than my grandson. We still can't understand him most of the time but he is finally trying to talk. I recommend that you have a second evaluation thru the school district. It costs nothing and if they recommend further treatment that will also cost nothing. I have been very favorably impressed with everyone from the school district and the treatment center. They are knowledgable, kind, sensitive, and caring.
One reason that I recommend a second opinion is that there may be something going on that isn't obvious or noticeable. However, I would start by questioning her current therapist, as another mom and also a professional, has suggested. Ask constructive questions and get helpful answers. Perhaps you will decide to continue with her, or not. I don't know your financial and/or insurance situation but if money is a part of your decision the school district evaluates and treats for free. (well, not actually free. Our taxes pay for it. :):):))
Speech is very complicated and involves muscles and nerves other than those in the mouth. It's best to get treatment as early as you can. The therapist may be seeing something that will be a problem later. For example, I was taught exercises to do with my tongue in first grade. One symptom that I can remember is that I couldn't curl my tongue.
It is your decision! Just get as much information as you can before you make it.