The good news is, she will grow out of this stage sooner or later. My daughter was the same way. She wouldn't nap unless she was in her car seat or bouncy seat until she was almost 5 months. All the books say, don't get them in the habit of falling asleep while moving...obviously the people who wrote them didn't have babies that wouldn't nap. Do what you can to get her to sleep so that you can rest yourself. Our daughter was diagnosed with reflux, and it was because of the acid in her throat that she hated sleeping on her back...also she would startle herself when we put her down (eventually that goes away). Once she started the medication for reflux, she was a new baby....sleeping for 2 hour naps twice a day and then mostly through the night. Also, I had to do the EXACT same routine every day before naps and bedtime, and put her in the crib while she was still awake, but tired. I would go in and reassure her every 15 minutes without picking her up if she cried, and eventually she learned to fall asleep on her own. I can't tell you how sick I am of "Good Night Moon"...but if I read anything else she won't go to sleep. Good luck! Hang in there!
J. W