Could my 3-year-old's visitation schedule with her father be affecting her sleep habits?
The average amount of sleep a preschooler needs is 11 to 12 hours per 24-hour day. That includes at least one nap. Whether or not a child is sleeping enough is not just a matter of numbers but how irritable, cranky, or overactive she is during the day. I have a feeling that the disruption in her life caused by your separation may well be interfering with sleep. If she is reluctant to nap, can you lie down with her? Sleep may represent instability and change rather than rest.
I hope you communicate directly with her father. Parents who talk to each other only through their lawyers can harm their children. Does she experience the same bedtime and the same bedtime rituals at both homes? If not, you each have to be willing to compromise. If this arrangement is relatively new, it may take her time to adjust, but the best advice is to coordinate what the two of you do to create as much consistency as possible.