I brought it up and although she’d never heard of it, I’m glad I brought it up as ‘limerence’ (instead of calling it a ‘crush’ or some other kind of relationship). It framed it as something I’m actively struggling with and not as something I should pursue with the LO. My therapist was very supportive and understanding. I also gave her the link to Living With Limerence, which helped me contextualize a lot of what I wanted to deal with, in my treatment.
Bring it up but name the term. Be honest with yourself about what this is for you (an obsession, as you called it) but be compassionate with yourself because it’s also a coping mechanism you’re obviously trying to work through. That’s why you’re in therapy! Good luck!
Limerence isn’t a “strong crush”. It’s a one-sided, (usually) unreciprocated fascination with another person you may or may not personally know or have contact with, directly. The book Living With Limerence gives a good overview on what it is and isn’t.
He's also written a book: Amazon link. It's very short—I'm about half way through it after one sitting—and very good so far, albeit fairly duplicative of the TED Talk.
Edit: Fixed link