My dog ate ants and threw up. Are ants toxic or harmful to her?

Without knowing if she ate the ants or what kind she ate, it would be hard to say. Most ants that crawl around on food tend not to be toxic, but some can sting or have toxic bites, and if she immediately threw up after, she likely purged them. However if you know the type of ant she ingested, you can contact The Pet Poison Helpline here: (there is a fee for this service) for more information -- https://www.petpoisonhelpline.com/

You can pick up her food and offer boiled rice and chicken for a meal to help settle her stomach if she seems otherwise OK now. If she continues to vomit, or shows other signs of illness such as extreme lethargy, pale gums or tongue, staggering or confusion, drooling, bloody diarrhea or vomiting, etc, then these are all signs of possible toxicity which should be seen by a veterinarian immediately.