It’s great….if she’s going to be 3 years old for her entire life.
I’d spell it Josephine, and use the nickname Posie. Because she’s going to be a cute baby for a heart beat and a grown adult for the majority of her life, and she may want to be taken seriously at some point.
Or not, she may go by Posie her entire life, and rock it. But she should at least have the option.
http://www.behindthename.com/pnl/56287