I think as long as your bub is sleeping through the night, the daytime naps are probably not as important. Our 3 year old has only just started sleeping through the night, in his own bed, without having to try tricks like taking him for a drive to get him to sleep in the last 6 months. We were at our wits end but he's good now. Our 6 month old is a dream because we didn't make the mistakes like rocking her to sleep etc.
She is getting tired obviously so I would suggest as others have said. Winding down. When they yawn or rub their eyes, give them a feed, put them down and get them relaxed. We've found, as bad as it is, that tv helps. Keep the volume down but I think the lights an movement tire their eyes and helps them go to sleep. My little girl will only watch The Lorax though, other cartoons or anything just won't do it. Lol I've seen it 1000 times I reckon and pretty much know it off by heart. Hahaha good luck.