It's weird, I only feel sick if it's visible. Or if it doesn't get mentioned. Like, pizza is fine, mac and cheese is fine (as long as no one says the 'c' word while I'm eating it lol). I never really liked the taste or texture anyway, so I don't feel like I'm missing out and it doesn't really affects my life. Except the time I went to Greece, and EVERYTHING had cheese. I was even dragged to a cheese-making shop, and I still cringe just thinking about it...blegh...
Honestly, it just got worse because my family used it as a joke for a while. They'd swing pieces of cheese in front of me and slip it in my food, so as long as you don't do that, she should be fine Like with any phobia, pushing it can make it a lot worse.