Yes, it is a sad day when the naps go away.
My daughter was in this napping "limbo" for a while. If she didn't nap, the dinner hour would be TORTURE, and if we sent her away from the table for her misbehavior, we'd almost certainly find her crashed out, sound asleep on the first piece of furniture she could lay her head on.
Your first response should be to maintain the "break" or "rest" time. How long she stays in her room depends on what you want that time to look like. When this first began, my daughter had to stay in her room the whole 2 hours. Then I started letting her get out about 30 min before her brother woke up for "mommy time." However, that didn't always work out because if brother woke up early, she didn't get that mommy time.
Right now, I send her to her room to play quetly while I put the 2 yr old down for his nap (which includes 15 min or so of "mommy time"). Once he's settled, I let her get up for a little "mommy time" where we chat about the day, do her homework (she's in preschool 3 days a week), or play a board game for about 30 min. Then she goes back to her room for about an hour to play by herself. Sometimes she'll even still fall asleep, but I make sure I wake her up when the hour is up.
I have a container of toys and craft things that isn't out much, so that's usually what I use to let her entertain herself while she's in her room. Stringing beads is a favorite, dry erase boards with washable dry-erase markers are good fun too, coloring, playing with her doll house, etc.
You definitely want to keep that time sacred!