My mom 75 recently starts to have bp over 140 every morning but usually comes down in the afternoon. does she need to start taking bp medication?

Probably a good idea: to get checked out by a health care professional. This is not a normal blood pressure. There may be a treatable reason for her blood pressure elevation and she would like to avoid the long term problems associated with hypertension (stroke, heart attack, kidney failure). See your health care provider and follow their instructions.