Quoting Chim Richalds:" Well then you can go the other way and wake her up earlier. You cant just put her in bed and expect her to sleep cuz you need alone time."
Quoting JackieCamps:" well, unfortunately naps are not gonna happen, we've tried... so what else should i do? is there like something she can eat or dirnk, like warm milk you think?"
Try to give her a glass of milk before going to sleep. Try to purchase also a bed that she would surely love so that she will loved sleeping in her own bed.
Does she come out of her room a lot at night during that time it takes her to fall asleep? I would try to stick with a time. Our 4 y/o does not nap and hasn't in a couple of years. He goes to bed by 7:30 or 8:00 at the latest each night (except occasional weekends) and then is up by 7:00 each morning.
If she is coming out then you need to tell her she can't come out anymore. If she is just looking at books and stuff I would put her in bed a little earlier to have that time to read and unwind. Maybe she needs that time to herself? If she isn't bothering you I would just leave it at that. She is 4 y/o, it's not like she is only 1 or 2...can't you guys enjoy your time while she is quietly reading and putting herself to sleep?