Is it normal that sometimes my baby slept with her eyes crossed?

Yes: You need to continue to monitor the eyes while awake as long as they stay straight it is probably ok . Ask your pediatrician to check your baby on your next visit. If you have any doubts get the baby examined by an ophthalmologist as a crossed eye in an infant can become a "lazy eye" and not develop connections to the brain correctly leaving the vision pemenantly decreased.

Crossed eye: Crossed eyes are not normal but can be present in the first few days of a young baby's life. If the eyes remain crossed when she is awake, see your pediatric eyemd for an evaluation.