My wife got her periods last 2 times every 15 days she is 48 what could the reason be?

Irregular hormones: This happens in perimenopausal women i:e just before a woman attains the latter. She should be fully evaluated by her physician to rule out other causes of irregular bleeding.

Peri-menopause: Irregular periods often are a sign of the beginning of menopause when the eggs no longer produce enough estrogen and progesterone to regulate the cycles. At age 48, it is entirely possible that your wife's periods will not become regular again. Have her see her physician who can do a FSH/LH blood test to see if she is in this transition, called peri-menopause.