I haven't read the other responses but here's my thoughts. Take what you want from it.

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Your daughter and I sound like twins. I have worried about things since I was a child. I would have panic attacks, make myself sick with worry, and just be inconsolable.
I vomited
every single day of 8th grade. Seriously. It was my routine. I'd wake up in the morning, eat breakfast, worry myself so much between leaving the house and arriving at school that I'd set foot on campus, go to the girl's bathroom and vomit. Then, I usually felt better but not always.
High school was the same way-- I worried about grades, getting into college, my friends, my boyfriend (now husband), etc. I was a mess. I cried and clinged to my mother. She did all she could, telling me "not to worry" but nothing makes a worrier more upset than being told not to worry. The only way my anxiety didn't get the best of me all the time was by being involved. Involved in leadership, with friends, etc. But of course, because of the anxiety, I didn't always want to be involved. It truly was a day to day battle.
College was miserable. I cried and cried and cried for months. I begged my parents not to leave (I went to school 4 hours away-- not too far). Finally, after another experience (date raped at a Frat party.. sorry if it's TMI), I forced myself to go to a therapist. And it has made a huge difference. It's definitely a process but my therapist has taught me various ways of coping with my anxiety. Sure, there are days when the coping mechanisms don't cut it but most of the time, they help slightly. That being said, the worrying doesn't go away but the severity of the worrying declines.
I personally chose to not go on medication but I definitely believe that it can help some people. Some days I wish I was on medication but I think I am managing my anxiety fairly well these days. However, I am completely open to medication for myself, in the future, if necessary.
Also, and I don't mean to start any fights, as I became more religious, the power of prayer and reading my Bible has helped me personally.
OP- again, I haven't read any other posts or your responses but I hope you got something out of this-- even if it's just to let you know that you and your DD aren't alone. My anxiety was and still is difficult for my mom to deal with-- she wants to help but as you have found, can't always make things better.
In my opinion, have your DD meet with a therapist. Make sure she knows that it isn't "embarrassing" to see one and that results might not come immediately but hopefully, she'll feel some relief. I'd also consider medication.
Best of luck to you and DD.. my heart goes out to both of you as I know, firsthand, how crippling anxiety can be.