I'm a guy and I don't see anything wrong with the dress. Typically it's been the therapists who have been told to dress properly and control their reactions, and patients are allowed to be comfortable and not worry about sending the wrong signals or people thinking the wrong things about them or acting on them. The only times I imagine a therapist would react to something like that openly is if what you were is an obvious deviation from what a person with your background or figure or sense of style would wear. Sometimes therapists (at least the good ones) would point something like that out to the patient, not as a judgement but to see what the patient thinks about this and if there is an intent behind it. Like a depressed person showing up in torn smelly clothes he hasn't washed in a month. Experienced therapists have seen a lot of different people and have developed more control over their own reactions, be it sexual ones or hostile ones. A passing glance does not mean the therapist is sexually aroused or distracted. People's eyes wander, and I think if you notice a pattern, why not bring it up indirectly, like saying you feel some men stare at you and it makes you uncomfortable and you question your choice of clothing even though you think what you're wearing is reasonable.

So overall I think it's considerate of you to not want such a thing to cause any distractions, all I'm saying is that don't spend too much time thinking about this. I think most people here agree that the dress is not inappropriate. My two cents.