Those annoying summer time hot spots! My name is Rebecca. I am a veterinarian and will do my best to help.
First of all, if you are not using flea and tick control, please start; these are a common cause of hot spots.
Hot spots usually respond to cleaning, antibiotics, and steroids. If you can clip the hair away from the spot, that is helpful. Clean gently with gentle soap and water and then dry the area. Apply topical antibiotics like Neosporin, as well as topical steroid cream like Cortaid or Cortizone 10. Treat a couple of times a day.
If it is a large or deep hotspot, then oral antibiotics and steroids might be needed. That would mean a vet visit.
If she has underlying allergies, antihistamines like Benedryl or Claritin may help.
Let me know if you have more questions I can answer. If this was helpful, kindly consider rating my answer!