My first baby never engaged either until labour - at my last appointment at 39+1 he was still 5/5 and didn't look like moving down. My Dr wasn't concerned as he said that not all babies will engage. He was born 5 days later, 1 day early and I had a trouble free 12 hr birth. He did engage once labour had established though, so your little girl has plenty of time to engage and if she doesn't that doesn't mean you can't have a vaginal birth either.