I agree with everyone else's posts.
If she is older or already vaccinated it might lessen the symptoms and severity of it.
*DO NOT GIVE THE STRANGLES VACCINE AFTER EXPOSURE!* It is very dangerous to do as now she is already developing a high level of antibodies after exposure and giving the vaccination could tip her over the edge and she could develop Pupura Hemorrhagica.
I actually asked my vet to give my horse a Strangles TITER when he was moving to a barn that required the vaccine (a test of the antibodies he had against the disease before giving the vaccination IN).
He ended up having enough antibodies (because of age) that it would have been dangerous to give him the IN vaccination. so she actually gave me a letter saying the horse had sufficient antibody levels to repel the disease and not be contagious. If I gave him the vaccination without the titer, he could have developed Purpura Hemorrhagica/******* Strangles)
as for other ways to prevent further exposure...
If they have an area to quarantine the healthy horses I would do that. disinfect stalls,brushes,buckets,hoses that they water the horses with,scrub brushes for buckets,stall forks any commonly shared items. PITA!
post a sign outside the barn door for any visitors that come by the barn (they could bring it back to their horses or barn).
Provide a bucket with bleach water in it or chlorohexidine to disinfect shoes after leaving the barn and have a change of clothes (if leaving to another barn) and shoe/boot covers like used at hospitals.
A lot of people forget to disinfect commonly used items for all the stalls like : hose,stalls forks,grain buckets. etc.
however IMHO. it is too late and she has already been exposed. Snorting helps the organisms travel long distances.
*Member of the Quality Free-Choice Hay/Pasture Feeders Society* *In Favor of Turning horses out as long as Possible*