Well, first, Slim Fast really isn't made for women, but yes they have a small amount of calories, about 180-220, and probably won't satiate you depending on your metabolism. If you're working out regularly, then you'll need more than just the Slim Fast.
You need to either actually eat breakfast, take a meal replacement shake or bar, or a combination of the two. It's your first meal of the day after you've basically fasted for anywhere between 6 to 8 hours, hence the name 'breakfast.'
If you want to eat food, you can save yourself time by making something the evening before and then reheat if necessary. And remember, you don't have to limit yourself to the traditionally thought breakfast food items.
If you're going with a meal replacement shake or bar, make sure it's got enough calories for you, probably around 400-500, and you're getting your nutrition's worth.
If you mix it between the two, my suggestion would be get your protein from the shake or bar, since most have quite a bit in them, like 20-30g, and the carbs from the actual food.
Food: egg white omlette with veggies on whole wheat/rye/pumpernickel bread. turkey breast/chicken breast sandwich with veggies in a whole wheat pita.
Meal replacement: Protein powder supplement mixed with milk or juice and frozen fruit.
Mix: Protein shake, 1 scoop, and an apple with peanut butter, or oatmeal with fruit.