What Causes Delay In Menstrual Bleeding After Sudden Weight Loss?

Question: Hello, my name is xxxxx and I am the mother to a now 15 yr old daughter who suffers from anorexia. Back in XXXXXXX of 2016 she was 70 kilos ( 154 pounds ) with an overweight BMI. She is 5'5 inches (166 cm ). She was very unhappy and I agreed to help her lose some weight. The goal we set was 135 pounds or around 60 kilos with weekly after school weigh ins. Anyway, it was all very sensible and she lost weight slowly at around 1300 to 1400 calories a day. It got obsessive around Dec 2016 and she dropped to 57.5 kilos or 126pounds. She did not get her period in XXXXXXX 2017 and I immediately took her to her GP and we began weekly visits to a dietician, the GP and a therapist. She quickly gained 5 pounds ( 2 kilos ) but it was not until March 28th 2016 that she had gained the 4kilos or 8.2 pounds that her GP and dietician wanted her to be at a BMI of twenty two. Please note that eleven at her lowest weight her BMI was never out of her healthy range. So she now weighs One hundred and thirty four pounds or sixty one kilos and has since March twenty eighth. She did not get her period in XXXXXXX Fed or March or April. The dietician thinks it should have come back in April because she got to her healthy weight. Her GP states it could take months for it to return. The dietician wants her to continue to gain weight until she gets a period. The GP does not want her to gain anymore since she is at a BMI of twenty two. What do you think? Please note she began menses at twelve years old and has regular periods for tow and half years until this. What is your opinion? Thank you, xxxx