Just like "human" diets, they will plateau for a time and you won't see as "dramatic" a weight loss during those times. IF she is muscling up, then that could account for her not losing as much as well. Muscle weighs more than fat, so her "fat" percentage could still be going down as her muscle mass increases. Use the "feeling her ribs test" a little more now than focusing on the numbers of how much weight she's losing.
GOOD JOB!!!!!
Debbie