Hey Squiggle.........=)

I don't think she will kick you to the curb or something like that. I'm sure you will get a understanding reaction. I was just sharing my thoughts and experiences on it.
I just find it interesting that it is bothering you so much. I think it's safe to say it might be bothering you more than it will her. Do you feel like you betrayed her somehow? Or broke her trust?
When I first did this, that is exactly how I felt. But now with the second T I do not feel that way at all. I wasn't looking his info up to use it against him in someway or to harm him. For me, the motive was to get closer to him, to connect with him. To find a way to calm myself outside of that precious hour of therapy each week.
Look at your motives behind why you did this. Your previous post about "a guilty conscience" concerns me. You really have done nothing wrong unless she told you "please do not look me up online". You may find you are not the first client that has done this on her.
I understand you wanting to tell her though...........I do think there is something deeper going on. I hope it goes well, I wish you the best. Be sure to let us know either way.