Sometimes a few minutes with a book is exactly what's needed to fall right to sleep. It's often the last thing DW and I do for the day, too. So, we allow it. DD can use the bedroom light, and she has a book light, too.

If you're concerned about reading too long, you can always check back later.

It may also be worth revisiting her schedule, because sleep needs do decrease as they age, and the sun isn't even setting until 8pm this time of year.