My gf has been off the hCG diet for a few months now. The diet seemed to thin out her hair at the front. Is this permanent? Can she get her hair bac

Probably yes. Severe dieting can cause hair loss. A healthy diet may help her get some hair back. It takes a while. Some people think that taking biotin and prenatal vitamins helps make your hair and nails thicker. No proof, but it probably won't hurt to try.
Probably. Hair loss is probably not permanent in these situations. In addition to biotin, borage oil has been helpful for hair & nail health. Inexpensive & over the counter.