From my experience (just started first year 14s), this is VERY true. It seems most girls I've run into are very reluctant to change their glove, and they think it should be floppy before you start to use it.A year before you will need one.
Our Center fielder has a new 12.5 glove. Still a little stiff, but definitely game ready. She is currently using an 11.5 baseball glove that is falling apart. One of the other girls on the team told her, she can't use the new glove yet. It is way too stiff. sigh.
Buy the glove at the year end sales and have it broken in all winter. By the end of the summer season, she might be willing to change. Or better yet, hopefully the old floppy one breaks and forces the move (that is what it took for my DD).