Bathroom light stops working after 2 days

My daughter bathroom has a ceiling mounted 2 bulb fixture. Last month the light went out so i replaced the bulb and everything was good until 2 days later the bulb went out again. I replaced the bulb it worked and a couple of days later the light went out again. I removed the bulb and plugged it into another fixture and it works fine. The GFI in her bathroom was not tripped and everything on the electrical panel in the garage looks fine . I am stumped on this one.