This seems to be a reaction to an insect bite. The nature of the insect, however, cannot be ascertained . It would subside faster with an anti-histaminic medication (taken as a single dose). You may consult your physician, in case your mother develops more such reactions over her body in the next few hours to days.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.