"The woman will be at the painting exhibition."
Translation:Η γυναίκα θα είναι στην έκθεση ζωγραφικής.
I'm not a native speaker, but I think that the problem is that "της" involves speaking about a specific painting, since it's a definite article, and "ζωγραφική" means painting in the general, abstract sense. So "έκθεση της ζωγραφικής" would mean "the exhibition of THE painting", which would be better translated as "έκθεση του πίνακα". Since "πίνακας" means a piece of painting. Please, any native there, correct me if I'm wrong.