A.T.
Hi MartyMOMMA,
She needs to learn to manage it. It is after all, stress on the body and she just needs to learn certain techniques to help her relaxation response come into play. Read below. There is no cure for it. You don't want to put her on meds for anxiety. Her entire response was probably brought on by the trauma of the collar bone and has never left her.
The counterpart to the fight-or-flight response, the relaxation response occurs when the body is no longer in perceived danger, and the autonomic nervous system functioning returns to normal. During this response, the body moves from a state of physiological arousal, including increased heart rate and blood pressure, slowed digestive functioning, decreased blood flow to the extremities, increased release of hormones like adrenalin and cortisol, and other responses preparing the body to fight or run, to a state of physiological relaxation, where blood pressure, heart rate, digestive functioning and hormonal levels return to their normal state. During acute stress, this response occurs naturally. However, in times of chronic stress, when the body is in a constant state of physiological arousal over perceived threats that are numerous and not life-threatening, the relaxation response can be induced through techniques such as meditation, yoga, tai chi, deep breathing exercises, self-hypnosis and other tension taming and stress-management techniques.
Yoga works really well for little ones, give that a shot. As she gets older, with the yoga in practice hopefully, meditation will help. Good luck.