First of all, we're sorry about the accusation menu being a little bugged. This was a very rushed development for a game jam and we weren't able to fix it in time. However, there's at least some advice we can give:
If you're unable to accuse Isadore, try waving your mouse back and forth over the LEFT side of the button to do so. For some reason, it's bugged from about her name rightwards.
If that fails, pick "not ready" and then talk to her again. If her accusation is already highlighted, then you can use the arrow keys and E to move and make your selection.