(Warning: I’m not an expert, just trying to help steer you in the right direction)
For one thing, I’m pretty sure that panic attacks when you have panic disorder do not have specific triggers. Someone might have panic/anxiety attacks with other anxiety disorders, though. Just do a little more research to differentiate between different disorders so you don’t give her the wrong thing.
I do not have panic disorder, but depression with a side of anxiety, and I have had anxiety attacks before. With my more mild ones, I only displayed a few symptoms- heart racing, crying, some hyperventilating, etc. I had my first bad one more recently, and it was kind of terrifying because I literally could not speak. I had been crying some beforehand, and I was really ridiculously nervous about something (it was finals week, and lemme tell you, a lot of stuff went down). My breathing was a little fast, and I was crying uncontrollably, and from there, it spiraled into an anxiety attack. My fingers and hands went numb, which freaked me out, and I started hyperventilating even worse. Then my face went numb. I was trying to tell my boyfriend what was happening (because I knew in this case), but I couldn’t communicate. After it did stop, everything was still numb for a good 10-20 minutes, and I don’t know how to describe how I felt other than “empty.” I felt really off for a good while afterwards.
As for comforting people while this is happening, some people really hate being touched. In my case, I preferred being held tight. Do not say anything like, “there’s nothing to worry about!” “Don’t be scared!”, etc because it’s kind of dismissive. What you should do is make sure they know what’s happening to them, try to help them get their breathing back to normal if you can, and be reassuring (bad example, but more of a “you’ll be okay” rather than saying not to worry).
Long post, but I hope it helps. I can try to answer additional questions if you have them.