I have never had to use any anxiety meds for my dogs, but I have had experience with a Dane with anxiety. (Meds were recommended but I opted not to do that.)
Connor had really terrible anxiety when I first brought him home from the pound. He was making himself sick. He had diarrhea (every day) from stress, and he could just not hold still, ever. He was a wreck.
My "treatment" for him was: First... put him on the best diet I could. I prepared his meals daily (fresh chicken, rice, oatmeal, veggies, supplements). I know not everyone can do this, but look at what you are feeding her and make sure it is the best quality food that you can afford. I am a firm believer that the better food, the better the chances of the dog being balanced.
Next, I looked at Connor's daily routine and tried to figure out how and where I could take away little stressors. One thing I did was stop taping up his cropped ears. That alone made a huge difference in his life! Next I stopped making him sleep in his crate, and instead I trusted him to a room with a baby gate and gave him a huge cozy bed. I think this also made a big difference! Those were just little things that I did, little adjustments, but they really helped.
Finally, I looked at exercise. Was he getting enough? And was he getting enough mental stimulation? So I made sure to go out in the yard with him every day, and just play with him!!
Run around with him, throw sticks for him, and just interact with him. I also did some obedience stuff! Just really casually, to get his mind working and give him the feeling that he could be a good boy, by obeying commands and then getting praised.
I don't know what your daily routine is with your dog, but maybe there are some little changes and adjustments you could make to help her out, without resorting to drugs. Before even trying St. Johns Wort (which is an herb) I would try Bach Rescue Remedy. It is homeopathic and TOTALLY safe, absolutely no side effects, and very easy to administer. You can get a bottle for about $15 that will last you a good while. That stuff is great. (I take it when I am stressed out too!!!) You can get it in any natural food store.
Now Connor shows no signs of anxiety!
I was worried for a while that he would not do well with my active pack of dogs, but by making the little adjustments here and there and just really trying to get to the root cause of his anxiety, I think I was able to really help him. I eventually weaned him off the home prepared diet and he now eats high quality kibble, and his digestion is back to normal. YAY!
Good luck with your pooch, and I hope you find exactly what she needs to be a more balanced and happy girl!