Sorry to disagree with the above poster, but thyroid nodules often DON'T change the levels of thyroid hormones. Mine didn't.
If there is pain or any discomfort, she needs to see an ENT (ear, nose, and throat doctor). An endocrinologist is only useful if her hormones are off. If she needs other treatment, she'll be referred to an ENT anyway.
Shohreh: I know you're worried, but if it is cancer, the likelihood that it is treatable are ridiculously high. They say that if you have to pick a cancer, this is the type to go with. It is usually removed with surgery and then she would be treated with what is called radioactive iodine treatment (which is nothing like chemotherapy or radiation, it's a 100 times easier).
The good news is that multi-nodules are more likely to be benign than if she only had a single one that was growing. She should continue to have sonograms and biopsies to make sure they continue to be benign.
My advice for you and your family is to do a ton of research into the topic so you can ask the doctor informed questions. Personally, I was less scared after they found mine when I understood what was going on and really participate in making informed decisions about what to do. There are a lot of resources out there.
More good news: if she does have to have her thyroid removed, either because it is something or as a precaution, she can live completely normally on hormone supplements.
If you have any more questions, feel free to post again.