Gastric sleeve and menstrual cycle

Let me start off by say my sister is incredibly stubborn and one of those people who won’t go to the doctor until they are forced to or have no choice. My sister had the gastric sleeve surgery about 2 months ago. Since she left the hospital, she’s had a “period”. Her “period” stopped for 2 days but resumed again. She had an appointment scheduled but then cancelled because her period had stopped. Now she refuses to go to the doctor. Has this happened to anyone after the surgery or any surgery not related to our reproductive system?