Hi, I'd like to help you with your question.
Panic attacks and anxiety respond very well to treatment. It can be therapy or self help, but doing both together is helpful as well.
Panic attacks and anxiety are caused when your body's flight or fight response is triggered. A person with panic begins feeling afraid. Their body senses danger so it releases adrenaline to prepare the person to fight the danger or leave quickly. But when the person is not really in danger, the adrenaline has no use. So the person experiences the symptoms of an adrenaline rush but has no where to use it. This is what causes the heart palpations, rapid heartbeat, sweaty palms, shallow breathing and other symptoms of a panic attack. Stress can also be a trigger. In your daughter's case, she may have felt stressed by her upcoming wedding and this triggered her anxiety. Once she understands how anxiety works, however, these kinds of triggers will has less effect.
Your daughter has now developed scary thoughts in addition to her anxiety. This is caused by her mind finding ways to scare itself. Her thoughts have been on danger mode for a while and are used to scary thoughts. So she is continuing to scare herself with "what ifs". Having these types of thoughts is very typical for someone with anxiety and they will not harm her. If she was going to kill herself, she would not be afraid. She would be focused on dying, not anxiety. And the feeling that something is physically wrong with you is very common for people with anxiety. That is often how many people discover they have anxiety in the first place. They seek medical attention when they have a panic attack. The doctor rules out a physical cause and diagnoses anxiety disorder.
There are many ways your daughter can help herself. Going back to therapy is a great option. She can either continue with the psychologist she sees or find someone she wants to work with on a long term basis. Medications can also help. But medications are to be used only so she can function until therapy and self help begins to be effective. Staying on medications does not cure anxiety and can make it worse, since certain medications cause addiction and dependency. And the original problem is not solved either by medicine. Therapy and self help are much more effective.
Here are some self help resources she can use to work on her anxiety and panic at home:
The Anxiety and Phobia Workbook by Edmund J. Bourne
The Cognitive Behavioral Workbook for Anxiety: A Step-by-Step Program by Bill Knaus Ed.D. and Jon Carlson Psy.D. Ed.D.
A Life Less Anxious: Freedom from panic attacks and social anxiety without drugs or therapy by Steve Pavilanis and Patricia Alma Lee
You can find these books on Amazon.com or your local library may have them for you.
Anxiety and panic are highly curable with help and patience. She will get through this and be able to live a panic free life.
I hope this has helped you,