K.B.
It might just be a phase she is going through, and with the summer days so long right now, maybe it's just harder for her to fall asleep. You could try some room darkening window shades, or try putting her down earlier (like 7pm) but if she is staying in her room, behaving herself, and not crabby like she's overtired during the day, I don't think it's really a problem. There have been nights where my daughter agrees to go to bed, but just isn't ready for sleep yet, so I let her look at books and read for a while as long as she stays in her bed and isn't calling out for me for one thing or another. She's almost 6 now and she's usually out within 15 to 20 minutes.