I think cutting the nap could be way forward, my 3.5 year old only has a nap when we are visiting rellies in Italy where he is expected to be awake until later (meals out with family etc). When he dropped his nap I remember that there were a couple of days where he fell asleep at 530-6 but soon adjusted after a few weeks. I fed him dead early, 1630, so I knew he hadn't gone to sleep without eating. She will probably wake up again at 7pm thinking that she was meant to be having just a nap, but just explain that it's night time and go back to bed. In my experience sleep issues usually take a few nights of hell but work out in the end. if she keeps getting out of bed then I would keep putting her back to bed with eventually very little communication (it's bed time) . Exhausting I know, but worked here! Best of luck!
As a side note I believe that like adults, different children need different amounts of sleep. My 2 generally do about 10.5 hours rather than a full 12.