"She claims that since tomatoes and oranges are very acidic, they make your body a more acidic place. This is complete nonsense, after these foods are broken down they make the body more alkaline".
Sorry but you are wrong and the author is totally correct. People with acid reflux for example, are advised to avoid acid-causing foods such as tomatoes, oranges and beetroot etc, as these do indeed create acidity in the body (which is often expressed as acid reflux, and/or red, itchy blotchy skin etc). Research has also shown that cancer tends to thrive in an acidic environment, and this is why acid-creating food and drink (alcohol, coffee etc) are best avoided or reduced.