When is she *my* rabbi?

Just a question I have while preparing for UJRs Judaism courses and communicating with the rabbi at my local shul.

I’m going to a reform shul .will be converting with them and all that stuff. My question is, is it something that happens? An event? Or is it something automatic when I choose to keep going? Do I ask her to be my Rabbi or what exactly is the process here.

I don’t want to overstep, and I’ll definitely bring it up when we meet in person in a few months, but was wondering if this something easier than I’m making it out to be or if it’s dependent on the Rabbi?