It sounds like she is getting more sleep than she needs, so I'd suggest either waking her up earlier from her nap (don't cut it out entirely, at this age I would keep it at least an hour, and would probably start at 1 1/2 if you're going to cut it down) or put her to bed a bit later.
As far as naps go, there is a huge range, usually sometime between 2 and 5 a child will no longer need a nap. If she is sleeping 2-2.5 hours at naptime, she probably isn't ready to cut it out, but you could shorten by waking her up early from it. You'll have to play with times to see what works. I wouldn't wake her up with less than an hour though at this age. If she cuts to less than an hour on her own without you waking her, then she's probably ready to stop napping and you can just try for a few days and see what happens.
As far as the toddler bed goes, it is not likely that changing her to a toddler bed will actually help her sleep longer. You didn't say what time they are going to bed, but she is obviously getting all of the sleep she needs or she wouldn't be waking up on her own, so I believe she's sleeping just fine. Generally, most parents move their children to toddler beds sometime between 24 months and 36 months, so you'd be fine to change her at anytime, it's really just at your discretion. Some parents even move a little earlier if their child is prone to jumping out of the crib and they have safety concerns. Remember though, once you move her to a toddler bed she'll be able to climb out on her own without any difficulty, so it may make things worse.