If your friend wants to eat meat again, that is her choice.
I decided to eat meat once about 20 years ago, after having been a raw vegan for about 8 years, and, so, after deliberating for a while, I went to a specialty hamburger restaurant and ate a hamburger. I did not die (duh), and I did not notice any untoward health issues (okay, granted, I was very young and very healthy). I did go right back to my normal raw vegan diet, simply because that is what I wanted to do. Meanwhile, I began to believe that all that talk about having physical problems if you eat meat after not having done so for a while is a bunch of guff. I do not know why people keep promoting that concept. At the same time, some people who decide to eat meat after following a vegan diet for a while have problems with dairy products (I have never been able to consume dairy products, and when I have tried to, I have had some "interesting" digestive experiences. Once, when I decided to go off vegan, and ate some ice cream, I did suffer, and once, when I was cooked vegan, I ate some supposedly vegan cheesem and had trouble - first, it tasted like milk, and second, because I am allergic to milk *protein*, i.e, casein, I had some ill effects)
If your friend is healthy and has no fish/shellfish, lactose, or casein allergies, the only *physical* issue she might experience, if anything, would be a "heavy" feeling after eating meat. Any other "symptom" would, most likely, be psychological (guilt, fear, belief system).
Choosing to eat meat works well for most people. If a vegetarian/vegan decides to go SAD, if it is her or his own decision, and it is what she or he wants to do, there will be no problem. Our bodies are pretty efficinetly designed to handle just about anything we put into them (think alcohol). If you choose to eat meat, your body will handle it. If you choose to eat a vegetarian, vegan, or raw vegan diet, your body may handle it better (as we are told)