I have been diagnosed with generalized anxiety disorder, panic disorder, and PTSD. Have felt this way my entire life, as has my grandma and sister, and so far there is nothing that takes it away. (except drugs) Most of the time my panic attacks are triggered by nothing at all, I'm not afraid of anything specific like dieing, but sometimes it feels like I might die if i continue to feel that way. I was prescribed 120 2mg Klonopin (clonazepam) a month and my tolerance was up to the point that I had to take that many, I am on nothing now because I wanted to get completely sober (except Paxil) and it is nearly unbareable but I am alive. There are a lot of different therapy techniques in dealing with these problems and a lot of experimental stuff too... I'd tell her to read about it on adaa.com or nimh.com- it helps to know the brain function behind it. Also tell her to cut out caffeine, nicotine, and large amounts of sugar. (caffeine is a killer!)
Also if you want to be there for her it is helpful for you to know what is really going on, and recognize that this is not "in her head" and is a very, very real physical reaction. (my psychiatrist explained it as your brain seeing a cat and thinking Dinosaur! and releasing a bunch of adrenaline in response) It can be very scary and the best thing is for someone to acknowledge it and make you laugh, distract you, help you cry and talk through things, watch a movie, (some say exercise but my heart rate goes so high anyway, it feels terrible to me)
If she has an addictive personality at all (anxiety can cause this A LOT) I would be weary of her going on Benzodiazepines (without therapy) because they work REAL well generally, and therefore the effect is greatly desired and relied upon. Instead of working through it ever, you just pop a pill. (plus the withdrawals are deadly and extremely unpleasant: very very very heightened anxiety) Feel free to PM me if you have any questions.