D.S.
All I can say is to remember that you are the mom and YOU decided when naps start, when naps end, and that she WILL continue to go to her room, get in her bed and lie there whether she sleeps or not! A child should never be the one to decide whether or not they should continue to take naps. My 3-year old also tries to forego naps, but I just tell her that it's not up to her and I put her in her bed. 95 percent of the time, she will fall asleep. On the days she doesn't, she stays in her bed until I say it's time to get up. My son took naps till he was 4 1/2. My daughter will do the same.
She's testing you to see if you'll forego the naps. Be strong, stern, and TELL her she WILL nap whether she sleeps or not and continue to put her down in her usual nap routine. If she gets up, put her back to bed and contine to do that until she realizes that she will not win that battle. Good luck.