What do you have to gain by telling her? What do you risk? Are the gains more than the risks? Do you want her to say it was okay and reassure you? Would you feel better (in backwards sort of way) if she reprimanded you or got angry in some way?
For me, knowing why I felt the need or urge to tell the therapist such a thing (it has a sense of confession about these sorts of matters) would matter.
If it was me, I would not tell the therapist