Hi,
sorry to hear about your sis, but as Jenna said, she is in the right place and she'll get treatment quickly.
There are lots of things that can cause aggitation and rapid heart rate.
Pain in the legs and arms can be caused by the hypoxia (lack of oxygen going to the muscles) associated with her heart racing. Same for the headache.
It is possible she has a heart condition such as tachycardia, which affects the electrical impulses to the heart.
It might also be 100 other things, MOST of which aren't going to be massively dangerous to her, so try to keep busy and don't worry.
Also, has she started taking any new medication lately? Anything from herbal medication to diet pills, not just prescription medication - sometimes these have very strange effects on the heart and circulation.
Keep us posted!