In most cases the residents of the city of Voronezh is called Voronezh. The representative of the stronger sex in this case – Voronezh, but the feminine of this form is not. Therefore, to refer to beautiful ladies in such cases is used to design "the inhabitant of Voronezh".
In the XIX century the inhabitants of Voronezh called "voronetiana" (in the masculine and the feminine – "voroniaky and voronetiana" respectively). But in the past, the twentieth century, residents felt that these unpronounceable names, first, outdated, and secondly, not very good sound. And they decided to known as the Voronezh – even at the expense of the loss of the feminine form.
Now the word "Voronina" still appears in dictionaries - sometimes marked "legacy", sometimes as a full synonym to "Voronezh". Nevertheless, residents generally prefer to be called "new" and sometimes very sensitive to attempts to call them "voronetiana". Therefore, despite the fact that from the point of view of the Russian language, both options are valid, it is better to use a more common and more modern form, calling the inhabitants of Voronezh of Voronezh. At least no one will be offended.
If you are not sure how to call the inhabitants of a city, you can just search Wikipedia for each city there is a guide, which among other things lists the valid names of the inhabitants of this settlement. In an extreme case, use a descriptive design, such as "inhabitant/resident of the city of N". The rules of the Russian language such a replacement is valid, the error is not considered.