Panel three Grace is very much relatable to me.
Tedd's naturally under no obligation to tell Diane anything about her gender, but Tedd is also aware that there are good odds of Diane finding out at some point. Of course, Tedd is also under no obligation to tell Diane immediately just because of that, and not telling Diane now is the choice she's making.
I think I wrote that how I wanted. Full disclosure, it's, like, 2:47 am when I'm writing this. I'm only sort of conscious right now.
In any case, yes, I am allowing limited sitcom hijinks to happen, so of course Grace has an imaginary ex-boyfriend named Tyrone now. That's how these things work.