I'd say put her down for her nap in her dark room. If she decides she wants to play, leave her alone in there for the duration of the wind down and the nap, so until 5:30 PM. Then just go in there and bring her out. If she absolutely won't nap, at least you can have her in a very low-key environment which may help her relax enough so that she makes it 'til 7 PM. The nap should definitely not last longer than 20-30 min, and not past 5:30 PM. By that time of day she should be tired enough so that she'll sleep by her regular bedtime or at least 30 min later.
If you put her in her room and she's fussy, again leave her in there until she starts to cry, at which point you'll have to do PU/PD. I would think that, after a few days, she'll go down for that nap, though, you never know with little ones, especially if she's as spirited as my ds.
As for the tea question, I'm not really sure. We don't do that here. Do you really give the baby tea? :?: If so, what kind? (this is just for my curiosity, not a BW question.
I hope this helps! Some babies can be pretty stubborn!