Hello, I Took My Mother, Age 72 To The ER

Hello,
I took my mother, age 72 to the ER last night because her left breast was swollen and hard. It appears when I saw it that she had a red small rash or blotch. I assumed it was an insect bite, etc. She had a mammogram done two months ago and all is benign. It's just perplexing how swollen it got. At the ER the physician indicated that it appeared it was a bug bite, but not sure what. She was administered two antibiotic shots and given a pain med. There was no sign of fever, normal BP, and no pain at loci. Doc discharged her with prescriptions as follow- Clindamycin, Neosporin, Tylenol Codeine 3, and Ondansetron. It's been about 24 hours and not much of the swelling has gone down. Breast is still a bit hard to left lateral area. I am just concerned and was hoping to see a dramatic change after getting home to see her today. Any advice??
Cris