If the new hens are not already in an established group ie they are strangers to each other, then your survivor will be just another stranger, so it would be an easy introduction with no worries about numbers.
If you aquire an existing group, then she will be the stranger and may have trouble integrating.
She will not necessarily be at the bottom of the pecking order this time, but she could be - there seem to be no discernible rules!
I once lost a clutch of ducklings when I had failed to put a cover over their pen. They were taken by a gull, which just kept coming back for more. Lesson learned!