This appears to be a good example of early localized Lyme disease
She was started on doxycycline, and if she tolerates it, will take it for two to three weeks.
Labs were ordered, mostly because she has a history of Lyme a few years ago, and I wanted to make sure that there was no likely co-infection.
From Dermnet: Erythema migrans, a red expanding patch of skin, is the most typical sign of Lyme disease and is present in 70–80% of cases. It usually appears 7–14 days (range 3–33 days) after the infected tick bite. It starts at the site of the tick bite as a red papule or macule that gradually expands. The size of the rash can reach several dozens of centimetres in diameter. A central spot surrounded by clear skin that is in turn ringed by an expanding red rash (like a bull's-eye) is the most typical appearance. Erythema migrans may also present as a uniform erythematous patch or red patch with central hardening and blistering. The redness can vary from pink to very intensive purple.