help with horse health?

[Rose]

i have a 12 year old mare that i have had for about 3 years now and have never had any health problems with her but the past week i have noticed hives on her. they started out on her withers and shoulders and then spreaded all over her body. i thought she just had hives and another horse i have had got them before so i fed him flax. well i was going to try that with her then today i noticed that she is losing hair around her face. there is an animal that has been coming in the pasture that looks like it has the mange but i havent been able to kill it. could she have gotten that from the other animal and would that cause the hives? she isnt acting like anything is bothering her. i would take her to the vet but dont have the money right now. any help would bt very much appreciated.