Hi forcegx7!
Thanks for stopping by! It's of course hard to give solid advice without knowing a lot more about your friend however there are a few things that came to mind when I read your post.
How is her diet? That's always a good place to start as well. It's sometimes difficult in our society to get all the nutrients we need, especially if we aren't eating organically grown foods and cooking a lot on our own. If she has a typical American diet, I'd suggest she look into adding more healthy foods and definitely investing in a whole foods multivitamin supplement (this is one that is derived from real food as opposed to synthetically made - your body absorbs this much better). Being anemic as well, she should definitely make sure she is getting the vitamins and minerals she needs.
Also, if she only gets physical activity when she goes out dancing and it isn't really a part of her daily life (if she is otherwise pretty sedentary), that could also explain why physically exerting herself with dance leaves her achy. Her muscles are simply out of practice.
I've reviewed a few books that have to do with increasing energy in one way or another. Take a look at this one,
365 Energy Boosters, which may give her some ideas on how to boost her energy levels and get her muscles more fired up.
I do hope this helps! Let us know if any of this works well for her!
Best,
Leah