My oldest was 22 months when he was trained, mostly on his own will. He refused to wear a diaper around 20 months so I got him some training pants (Fuzzi Bunz Trickle free trainers, we use cloth diapers so these were an easy choice for us) He wore those to bed and regular undies during the day, and he had it down in no time!
My youngest is 15 months, also in cloth diapers but hasn't pooped in a diaper for hte most part sinceh e was 6 months old! He would cry, scream, fuss until we took the diaper off and he would poop. Around 9 months we started putting him on the toilet to poop and now at 15 months he signs potty and we take him in. His diapers are rarely wet, but seeings how they are cloth we just keep using them since undies would be way too big on him!
If she is showing signs, go for it! Be prepared for accidents and be patient and consistent.