Hi. My Sister , 11 Years Old Got Her Periods

Hi. My sister , 11 years old got her periods for the first time the start of this month. It continued till 10 days. She got it again after a week with excess bleeding. We got a check up and ultrasound done. The doctor said everything is normal and just gave Pause tablet to stop the bleeding along with some vitamin tablets. The bleeding stopped after three days. She got it again after a few days and this time it is very severe. The doctor told her to continue pause tablets.it's been 4 days but she is still bleeding excessively. When we went to the same doctor again she gave her glucose and vitamins syrup too. She is also so weak that she can't sit for more than 5 min. Can you please suggest on what can be done? Thank you