Natural Remedies for Difficult Menstrual Cycles

My daughter (12 in just a few weeks) began her period last fall. Her cycles since then are close together (about three weeks apart - this last one just shy of that, I think), and relatively long (about a week). I had expected her to have a much lighter experience in the beginning, being so young, and have felt badly for her. But worse than that is the fact that during her periods, she practically turns into someone else. She has really rough mood swings, but usually only on the negative scale - from depression to anger - and is not very rational or reasonable during that week. In calmer moments, she acknowledges this, and bemoans how badly her period makes her feel. Physically, she doesn't have a lot of abdominal cramping, but she has backaches, headaches, and leg cramps. Often this all sneaks up on me, and when she crashes through her day like a dragon, I am frustrated with her, until she finally says something about it being her time of the month, and then I feel badly about not being more sympathetic. Last night after a really rough day, I realized I needed to get more serious about trying to help her through this. Because she is more independent these days than my younger children, I think I forget sometimes that she needs attention and TLC, too, and this is something she particularly needs help with.

So - any ideas or suggestions for some natural remedies that might help her? I have read about some herbal remedies for PMS, but I am not sure what she can use, being so young, and PMS doesn't seem to be as much a problem as the week of her period itself, being so frequent, long, and intense.