Hi everyone, I wanted to know if anyone can tell me if it’s normal for a 13 yrs old to have their period for 3 weeks straight every single month?

This has been happening ever since she started her period at 11 or 12 yr old not so sure, but she told me she’s tired of it and can’t take it anymore. I mentioned it to her doctor, but he just said is normal because she’s new at it. Idk what to do. I feel bad for her. And she’s taking iron bcus of her anemia.