What time do you attempt to get her down for her nap? What I might suggest is put a few books in her crib, maybe a lovey and then set the groclock for whatever time you want her to rest until and just leave her in her crib. If she's crying, obviously go to her but if she's just calling out for you, at best, I would open the door to her room once, maybe twice and just say "This is rest time, you need to lie down and close your eyes. I'll come get you when the sun is up." I would only do that for the first 2 or 3 days and then not go in any more. It's going to take a while for her to adjust to this, and you'll need to be consistent but a 30 minute rest at 4pm is too late. Ideally you'd want her laying down for an hour around 1pm. If you can get her to do that, then perhaps you could lengthen the time by 15 mins over a few weeks until she's napping for 1.5.
On days she will not nap, I'd aim for her to be in bed by 6:30pm, no later.