15% on a woman, is like 8-9% on a guy (women are naturally about 6% higher-than men)
as for cardio, have you ever considered slow-go cardio, i mean 55% HR for 45-1hr
or 20-30mins of slow-cardio after weights
currently im trying to break a plateau, and incorperating 7 cardio sessions a week, (i still take a day off

) however they are all low-intensity, i aim for 110bpm, although this is my first week doing it, i belive its working, low-intensity cardio targets the fat, and saves carbs, so your muscles will look fuller, and of course, who wants to burn carbs when you can burn fat