Having feelings for a T or p-doc is different than having an actual relationship. If a line is crossed, that's on the professional (T or p-doc), not the client.

That being said, it's quite common to have feelings of some type for a T, whether erotic/romantic or more maternal/paternal. Assuming the T is ethical--and feels OK discussing it--talking about such feelings can be beneficial to therapy because they're often rooted in something a client was missing in childhood and/or is currently missing in their adult life. Talking it through with a T can help unlock those needs, which the client may not have been even aware of until the feelings for the T came about.

That's definitely been my personal experience, having had both erotic/romantic and paternal transference (generally at different times) for my marriage counselor. I'm lucky in that he's both very ethical and also comfortable discussing the topic with me (and yes, my husband is aware, and we've discussed it in session). The erotic part helped me realize some of what I was missing in my marriage--empathy, someone who really listened and seemed to understand me, etc.--and realizing those needs were there helped me and our marriage (since then H knew what I was looking for). There's still a long way to go, and H is never going to be the empathic, sensitive, good listener that MC is, not just because of personality, but also because he sees me for more than an hour a week. Plus I was projecting a lot onto MC and idealizing him, and his talking about, say, what he's really like as a husband and father has helped the transference fade to some extent.

Again, as long as a T is ethical (that's really important) and comfortable discussing the feelings, they can be beneficial. Certainly painful at times (as I learned), but ultimately, for the most part, lead to some helpful revelations and understandings about oneself. YMMV, of course...