How long does it take for the flu to pass?

My husband was talking to his mother yesterday and she told him she was home sick with the flu. We are due to have our son via csection on the 19th but the doctor might push it back to the 15th. Last week me, my husband, and our 20 month old daughter got the flu shot to make sure we are all prepared for when our son gets here. Anyway my mil,as of yesterday, has the flu. How long would she be sick for? Should I ask him not to have her visit the baby for the first couple wks after hes born? Or might she be good by the time hes born to visit him?