I think every child is different. The sleep books I've read say around the age of 3 is a good time to transition from a crib to a bed, but both of my girl moved around the age of 2.
We had to try three times with our eldest. She kept getting out of bed and not falling asleep until very late. It was making her overtired and cranky, so we would wait a week or so and try again (her little sis needed the crib!). With my youngest there wasn't much effort involved because she wanted to sleep with big sis. Every kid is different and you'll know whether the time is "right" or not by the degree of difficulty you are having.
Some tips: ask her if she wants to nap there and let it feel like her decision. Make it a fun milestone to being a big girl. After a few successful naps you might ask her at bedtime where she wants to sleep. I would put the focus on her and refrain from mentioning that her crib is going to be occupied soon! We also put a body pillow along the side of the bed that was against the wall and that helped my daughter feel more secure (she was afraid of the crack) and kept any books or animals from falling back there.
All my best to you - I send you tons of patience!