Hello L.,
It could be that your daughter is finally old enough to not need to sleep as soundly at the beginning of her nap as she used to and now she is "catching" you trying to leave her alone in her crib. Since she is used to falling asleep nursing at night, you could try nursing her to sleep on the floor for her nap. I used to put a sheet down and a pillow for myself and rest, visualize, meditate or even fall asleep during my daughters' naps. Sometimes, she released my nipple in her sleep and I got up and read or worked on the computer near her until she woke.
Babies are really smart and instictively know they are safest in our arms or near our bodies, especially when they are relaxing into sleep. Babies are soothed by our presence and when they ask for us to be with them and we don't come, they will eventually give up and stop asking. They will learn to be comforted by "things," rather than by people. They also may not ask for the help they need in relationships, because they learned long ago that it was useless to ask. This is a deep wound.
My childrens' "schedules" change frequently as they grow to meet their changing needs. I am most successful by following their lead. If your daughter seems comfortable with one nap a day, then I would focus on supporting her in that direction. She also may sleep more soundly having one nap a day, rather than two.
You might also be interested in reading, "The No Cry Sleep Solution," by Elizabeth Pantley.
Enjoy your journey. ~T.