Hi Deborah,
That is tough. But I know exactly what you are going through. When my daughter turned 3 (she is 5 now) and in a toddler bed, she woke up EVERY NIGHT around the same time, which was usually 3am and again an hour later. What I think was the problem was the transition from crib to bed. I didn't deal with it too well since it was exhausting so we would just have her join us in our bed...not a good idea haha since she would then try it out every night.
Was she a good sleeper before she turned 3? My daughter was an super sleeper as a newborn till we transitioned her to a toddler bed. Then the games began! (-;
The good news is, they do grow out of this nonsense. I also think that napping can mess them up.
How about walking her back to her room and lying with her for a few mins. Tell her you will be back in a few mins to check on her, by that time (hopefully) she has drifted back to sleep. That helps when my daughter wakes up now once in a while.
Hope this helps?