I think that attachment can be good or bad, with therapists or anyone else. I think I would consider it a healthy attachment or just liking your therapist if you were happy and satisfied with what you were getting from her. You might look forward to therapy and even miss talking to her when you were not in session. But you are ok with just having her as a therapist.

On the other hand, I would consider it somewhat less healthy or more obsessive if you wish that you and she could be friends, or lovers, or something other than a therapist-client. I think that would result in longing and a lot of pain because your logical mind knows that you can't be friends or lovers, but yet you still want it.