It may be that she doesn't need an afternoon nap every day anymore. I know it sucks because you were used to have some peace, but they grow up and it was bound to happen. Honestly if she doesn't look tired don't even try. If you make her sleep even if she doesn't need it she'll start pushing back (welcome to "terrible two" age). She'll start hating going to bed even in the evening. When mines started growing at a certain point they were having a nap only on the weekends.
I'd advise against "let's try and see if you need one today without pushing too hard" because she WILL learn that if she just doesn't you'll not push back. You need to judge if she needs one (looks sleepy/extra cranky) and you have to put her to bed (and be firm) or not even try.
It might be that on days she doesn't have a nap she'll need to go to bed a little earlier (like half an hour earlier).
But I strongly suggest you don't make the "you need to sleep" routine a fight or they'll make it hell for you.