Sleep pattern is off
A normal, healthy 4 year-old who has an odd sleep
/wake cycle isn't always a problem, unless she is fussy during the daytime due to fatigue, falling asleep throughout the daylight hours, has frequent snoring, etc.
.. She has no job hours or school hours, so she may be fine sleeping whenever she wants to. Sometimes, a visit to the pediatrician +/- referral to a pediatric sleep specialist is helpful.