The value of alpha agonist in this case would be less treating the neurohumeral causes of her symptoms (i.e. inflammatory mediators, cytokines) and more just treating her severe vasoplegia that is a result of them. I have to say that I'm surprised metaraminol is still being used or talked about in EM/pre-hospital care, as it is largely ignored in my neck of the woods in CC and by the anesthesia folks. Having been away from pre-hospital/emergency/trauma care for many years, I can't really comment on the reasons for this.
That being said, vasopressin, which every ALS ambulance has, is an excellent treatment for vasoplegia and hypotension refractory to pressors, inopressors and volume.