15 month old taking off diaper

My 15 month old will not keep her diaper on if she doesnt have pants on. I don't think she's ready to potty train. I have a little potty for her but she does not like to sit on it. What are your thoughts? Do you think I should attempt to start potty training? If so, how can I get her to sit on the potty? or do you think it's just a phase and I should keep pants on her or discipline her when she takes it off consistently? Sometimes she thinks its just funny to keep taking it off.