How to get my girlfriend to stop being so stressed?!

I took a health class, and all the signs of Stress are Headaches, stomaches, and problems breathing/asthma. And my girlfriend seriously has them all, and I was wondering, how do I get her to just relax? I'm kinda tired of her always being so stressed out, because sometimes she gets so stressed out, she crys really hard, and that makes me extremely sad that I can't make her stress go away.. Is there any types of physical therapy for this? I need at home types, please.