My daughter is 4 yrs old She left drinking milk from

Patient: My daughter is 4 yrs oldShe left drinking milk from bottle a year back.From couple of months we noticed that during sleep she is making sound like she is sucking,initially we thought that she was hungry, but even when she is not hungry she is still macking that sound and her mouth open n close like thatToday morning we found a white liquid like milk was oozing out of her mouth, it was not vomit n not milk,What could be the reason??