J.L.
My son was 20 months when we finally gave in and let him start suing the big potty. So, no it's not too early. Just work on being consistent. Sit her on the potty in the am, and after she eats, right before bed. We started using pullups, so it was easier than putting a diaper on and off, and easier to be consistent. Other than that you're doing great. Definitely continue not to make a big deal when she doesn't go. Trust me she will fight back if you do! Keep at it!