Delphmoon, my DS is 17 months so a bit younger than your DD and he's hardly ever had two naps a day. So, I found that if on the occasional day that he's had 2 sleeps (second one after 3 pm), he'd be firstly going to bed later than normal, say 8.30-9 pm, and secondly he was a lot harder to put to sleep. But, if he only had the one nap and didn't sleep past 3 pm he'd be good to fall asleep by 7.30.
He now has a 1.5 to 2 hour nap every day around 11 -11.30 am (longer naps these days as he's more active). But what I wanted to say is that he's usually been quite good with going to sleep at night but about 4 months ago he was impossible to put to sleep even with the one nap, it would literally take me an hour to 2 hours to put him to sleep. Then one day about 3 weeks ago he's gone to bed with no probs again. I'm guessing it was his molars, but now he's back to normal so I'm very happy. GL hun, they change all the time, you just have to remember this will pass! I would def. cut out the afternoon nap. Just maybe give her some books in her cot to have a look at with some relaxing music so at least she can have a little rest without going to sleep in the afternoon.