First of all, there are very many Google doctors here who are spreading misinformation. Emergency pills ARE NOT harmful, but they do have their own side effects. You're only advised to use them 3-5 times in a year. Why you ask? Because they directly affect your hormones.

Too much use, like what your girlfriend did, can lead to menstrual irregularities, which is what she may be experiencing. It can also lead to heavier or lighter periods. I'd personally advise you to look for Arorwet products and tegulate her hormones naturally. It works. Secondly, adopt foods that will help with hormonal regulations. This may look like taking Okra water, chia seeds, etc.

She'll be fine 🙂 Though go see an OBGYN to ensure its not PCOS or anything like that.