Hi there,
Naps can be a tough beast for sure!
Do you have some sort of nap routine so that it starts to signal to her that it's nap time? Some babies are really sensitive to daylight making them want to nap and so a nice quiet, dark room might be helpful and perhaps some sort of white noise or soft music might help to tune out daytime noise.
Also, it sounds like the holding during naps and nursing to sleep has created a sleep association where she's only able to settle when these parts of her nap routine are in place.
It might be worth a try to recreate your night bedtime routine to signal to her that it's time to go to sleep. Do you nurse her to sleep at night as well? Have you been able to nurse her just until she's sleepy and then place her in her crib- sleepy but still awake? This is one of the most common ways to try and break the sleep association cycle as well as teach her how to fall asleep on her own and in her own bed.
If you haven't already, I recommend you check out this post on Sleep Associations as well as get a copy of Nicole's Guide on Common Napping Mistakes. Please post back with any additional information or other things you have tried and hopefully we can get you and baby on the right track!