Brainwash her

You activate your mind control ring, but wait for the shower to be over before giving Cynthia any commands. After she gets dressed, you give her detailed instructions to follow. First, she will go home and call her attorney and file for divorce. Then she will head to the address Robin had given you and wait for Robin's husband to come home. You show Cynthia the picture of Robin's husband and tell her that she'll fall in love with him once she sees him and spend the rest of her life with him.

When you're finished, you send her on her way. Still naked, you fumbled around the locker room for your invisible clothes but you can't find them. Giving up, you teleport back to the mansion and text Robin the details, leaving out the part where you had sex with the woman you had found for Robin's husband. As for her husband, you would have to take care of that at a later time.

It's still early and there's a few hours to kill before Robin returns, so you find another set of clothes and head out.