You need to schedule a doctor apt. for her. It may take a few days to get in and if she is still bleeding by then, then you know you didn't call too early. If she stops bleeding and there are no complications before the doctor's appointment, then you can always cancel. It may be normal for her and she turns out having regular (5-7 day) periods every 28 days or so, but it could be a sign of other issues. If her periods become worse or symptomatic, then reschedule the appointment. There are lots of things they can do these days to make life easier.
I had horrible periods (and still do). My first one was so bad that the doctor put me on a month's worth of birth control pills to help regulate and control my bleeding. I had horrible bleeding and cramps every month that I had to stay home from school on the first day of each of my periods. My parents only took me to the doctor the first time. After years of dealing with what I thought was a "regular" period and then struggled with infertility, I was finally diagnosed with PCOS (polycystic ovarian syndrome) a couple of years ago.
I know it is early for your daughter, but I highly recommend recording your daughter's periods and looking for signs of abnormalities. It could save her years of pain, embarrassment, and when the time is right, infertility issues.
I wish your daughter the best!