Long gaps are quite common. I know of several siamese who have gone days between kittens, so a break of several hours is fine, especially if she has stopped pushing. One of my girls had one kitten, and then just stopped seeminly happy, but there was definitely one more in there. Anyway the upshot was he was born three days after his sister by caesar.

How big was she? It could be she does just have the one kitten, sometimes if you stroke their sides you feel lumps but they aren't kittens just displaced insides that move gradually back. If she is quite settled with her baby then that may be her only one. I would take your cue from Mum if she is happy and well and not distressed or restless in anyway, then its a waiting game. If you are still unsure or she changes then ring the vet for some advice.