Some hens crow, or attempt to. I've got one that does it occasionally (and I also have roosters). I think they do it for the same reasons as roosters, it's just a way to tell the world 'here I am' and 'isn't life grand'. That hen isn't that loud and I've got some who's egg song is WAY worse than that! It may be temporary and she'll eventually stop. If she's doing it real early you can try blocking daylight into the coop until later in the morning. Unless your neighbors work nights and sleep all day, I can't understand the issue. I've got crows and jays that make more noise than that. Usually ordinance's cover roosters only, but check yours to see what is really allowed.