After wearing high heels out on the town for an evening, my girlfriends left middle toe has been numb for the last two days, should she be concerned?

Impingement : She may have impinged a nerve near the ball of her foot. Although she may not have had pain while wearing heels at the time, the wear and tear afterwards can swelling and impingement around the nerve serving her third toe. Rest, ice, antiinflammatory meds and wear supportive shoes, if numbness continues after 1-2 weeks, tell her to see podiatrist. Best of luck! hope this helps!

May be: This is typical of (morton's) neuroma which is an entrapped nerve. Avoid wearing high heels for a while and see if the numbness dissolves. If not she may need further treatment such as injections and/or surgical intervention.