Having a fetish is usually not the issue, the real problem is how you explore it, and how it affects your life. your therapist may just be a bad biased professional (I've noticed that many of the female therapists that I've worked with tend to disagree with males exploring any kind of fetishes) or she is seeing something that we don't.
Foot fetishes are in the very low end of the spectrum, it's somewhat common and is usually healthy. however, that doesn't mean that It can't be detrimental.
I'm going to be honest, we don't know the full story so throwing random encouraging claims about how good fetishes are is not healthy.
I do agree that fetishes are usually not an issue and are perfectly fine, almost everyone has one, but we can't ignore the fact that some people basically ruin their or someone else's lives with even the smallest of fetishes explored in the wrong way.
So in the end you should ask yourself how much is this fetish affecting your life. It's usually nothing, so don't worry too much about it, but you should also ask your theraphist why she thinks that way, listening to multiple perspectives is always better.
