either Yeast infection or she is ovulating and it's normal pussy discharge (you know, when she ovulate, her pussy will give more discharge for lubrication, you know to get fucked).
Be a man, do her laundry, ask question about stain, tell her it's good and you don't mind cleaning her dirty stuff but she needs to tell you how to clean it (sometimes cold water, sometimes hot water).
At your age, you should know what a cumstain looks like and this ain't
