My son is 21 months old and we're potty training... even if he pees, he brings me a diaper, he HATES being in a dirty diaper. Each kid is different. My point is, age means nothing, it's all about them being ready.
If you'd like to begin potty training but SHE'S not quite there yet, I'd get her in a big girl bed NOW. This was, when she IS ready to potty train, you're not throwing 2 things on her at once, and she'll be able to get out of bed if she has to pee at night. It would make for an easier transition.
And it's not too early to put her in a big girl bed... my daughters were 9 months, then 10 months when they went to the toddler bed. My son, he's still in a crib, which I'm kicking myself about because he wants to use the potty!!