Sleepless Nights at 3 years old?

I am hoping someone will have some good advice on how to handle my three year olds night owl acts. For the past several months we have had a heck of a time when it comes to bedtime. We start bedtime at 8:00, 8:30, or sometimes 9:00 (depending what we have going on). And at 11:30 we are still battling with getting her to stay in bed! These last couple weeks have been getting worse. There have been nights where it is 12:00 even 12:30! I have tried no nap in the day in hopes of getting her to fall asleep earlier. No luck. She has been in a big girl bed for over a year and a half now and this just started several months ago. She has been having a runny nose the last couple days so after her bath I have give her some medicine and this doesn't help her fall asleep either. Then the mornings are like WWIII around here! I have to get her up (who knows how long she'd sleep) and get her to daycare so I can get back home to work. I have talked to my sister who has had talks with Karenza, and that worked for a couple nights. I thought if it came from someone else beside mommy or daddy that it might work. I would say to her "Remember what Auntie Holly and you talked about? Don't you want to make her proud of you?" The first couple nights worked, and she would wake up saying "Auntie Holly is going to be so proud of me!" I have threatened to take toys away (and have followed through!), have threatened that she needs to get rest so she won't be sick or she won't be able to stay in a hotel and go swimming this weekend. There are times where Randy and I are so tired but one of us stays up to make sure she is sleeping before we go to sleep. She plays with her toys or "reads" books in bed. I realistically can't take all her toys out of her room because I have no place else to put them. She plays in her room all evening when she gets home from daycare so it's not like she doesn't ever get to play with her toys. I have run out of options. Do any of you with kids have this issue? It takes away from my night with my husband for us to talk about our day, and it takes away from just me time. I don't know what to do with her. She is a great kid, and she is fully potty trained (even through the night). Any suggestions, tips, or advice would be greatly appreciated as I dread our bedtime routine. Have a great week!