It's just that I am more hung up on BF than scale weight. I use a BIA monitor daily (which I know is out) then take the average of the British Army/US Army/US Navy ones every month when I measure just to get some sort of perspective. Another way is by eye (I posted a link to a group of pics on here a while back).
But I think it all depends on body type & personal perspective really. At the end of the day, if you are losing scale weight & eating the right amount of protein then you must be losing BF
PS for a female to show abs you need to have really, really low BF - its much easier for men