This happened to us, too. Went on for a couple of days if I recall and periodically after that. This was during the time we were transitioning dd from our bed to her crib (which took a full month and we're now 2.5 months from when we started). So, I would tell her it is not time to play, but time to sleep, grab a comforter and pillow and lay down on her floor and go back to sleep. Or dh would do it. But, she was not allowed out of the crib. But, inevitably dh would cave, bring her to our bed, get kicked in the head and then take her back. So, ultimately, popping a squat on the floor in her room taught her it was time to sleep and that's what everyone was going to do. For me, I felt ok with this approach as I believed that dd had the capacity to understand what was going on and that it was time to sleep. Demonstrating that by going to sleep in front of her would reinforce that lesson in our book.
HTHs!
ETA: I just read the post before mine and I should add that dd was a horrible napper for the longest time. All we'd get out of her is the 40 minutes or so you described. Now, she takes 2 naps. The late morning/early afternoon nap can last anywhere from 1-2 hours and the late afternoon evening nap around 45 minutes. That can be as late as 5pm. She's in bed by 9pm and usually up around 7am or as late as 8. If she's with her caregiver - the nap is a no-go and I come home to a fussy toddler (which totally sucks). I'd be more inclined to think it's the developmental milestones waking her up and not change the bed time. Are you putting her down for a nap when she seems tired as opposed to the time on the clock? If you are, I'd just suggest waiting it out and sleeping on the floor in her room in the interim. Not a great suggestion, I know, but it worked for us.
Elisa