I understand your reticence, as the pill causes so many problems for some women, and of course it is introducing hormones at a level which isn’t natural. On the other hand, some women get on really well with it and if she’s suffering as much as she is, she definitely needs a solution.
You could offer her a trial of the pill, on the understanding that it might work well and quickly, or she might need to go through a period of trial and error to find one that suits and solves her issue.
I’d be tempted to look at the bigger picture first, though, as other pps suggest. The pill won’t solve the underlying causes of her pain, though it may well provide temporary relief while she takes it. And if the pain is indicative of bigger issues that could affect fertility, it just kicks the can down the road, albeit she is young at the moment. Painful periods are common but NOT normal, despite what we are often told.
As well as the dietary changes pp mentioned, some women find that acupuncture can help enormously to balance and regulate hormones. Would that be of interest?
Ultimately, at 15, it needs to be her own choice, of course, with you helping her weigh up her options.