12 is a little shy of what is recommended. I would say too if they are pitching fits and a total wreck late afternoon she definitely needs her nap. If she is fine put her to bed at 6:30ish or 7pm like you are and see how she does.
All kids are different. Both of mine needed lot's of sleep and still do. My four year old sleeps almost 12 hours a night now. My seven year old 10-11 hours a night.
I think gauging her moods is the key.
If she is hard to handle in the late afternoon, put blackout shades in her room, start naps closer to noon and do music and a story and tell her she needs to close her eyes (don't mention sleeping), then walk out. If she talks the entire time and is up then I am with you in getting her.
You cannot force her to sleep, but I would adjust her bedtime.
When my son was almost three he gave up naps, so I told him if he wouldn't nap then I would move up his bedtime to 6:30 for a good year he was in bed asleep no later then 6:45!:)
If he did nap during the day he wouldn't go to sleep until 8:00 or so, so I knew he was fine giving them up.
His moods were grumpy for a while adjusting to the not napping but he was fine after a few days, we got through dinnertime and he would head to bed then.
http://www.babycenter.com/0_how-much-sleep-does-your-chil...
Here is some information, always talk to your Pediatrician too. Overly tired can backfire and seem like they have energy but they are wired. Lack of sleep can lead to lower immune systems, growth issues and moods! :) So good luck and just see how she does without naps. I had mine do "quiet time" before we really gave up naps and if they talked or sang or couldn't sleep I brought them back downstairs in about 35 minutes. If a child is tired they should be asleep within 15 to 20 minutes.
Good luck.