I'm a guy, not a girl, so this might not work for girls. But what worked for me was adding a little bit of lifting, decreasing my carbohydrate intake (not eliminating), really stepping up my vegetable intake, and consuming herbs and spices in copious quantities.
I'm still experimenting with that last part, but I seem to have stumbled onto something that may work: rosemary and cloves. I don't know if it's the rosemary, the cloves (the spice, not the cigarettes), or the combination, but 3 out of 3 times so far I seem to wake up the next morning thinner despite no other changes in routine. Not a trend, I know. Not statistically significant scientific evidence, I know. But I'm going to keep trying it, and maybe it'll keep working. Sprinkling ground rosemary onto a sandwich is easy. The difficult part comes with putting a heaping teaspoon of cloves into a 6-oz. glass of water and chugging it down.
With the carbohydrates, though, there are tons of things people eat that they shouldn't be. Beer = fail. Tortillas = fail. Corn chips (or any chips) = fail. White bread (whether it's "Italian" bread, sandwich bread, rolls at a restaurant, etc.) = fail. White rice = fail. "Juices" that have any sugar added in the ingredients = fail. Cappuccino/frappuccino/whatever-your-coffee-purchase if more than coffee beans and water go into it = fail. Cakes, pies, cookies all = fail. What's left? Whole-grain breads and products (which is more than just wheat, oats, or oat bran -- there's spelt, amaranth, teff, and others), quinoa, brown rice, bulgar, vegetables, and fruits & true fruit juices. This is not to say that I never eat a cookie, or celebrate a friend's birthday with a slice of birthday cake. However, it happens like once a month, not 3+ times a week.
I also eat NOTHING that is deep-fried, and I NEVER buy a product if "partially hydrogenated" is on the ingredients list. The last one is harder to eliminate than you think, since some restaurants use partially hydrogenated soybean oil in more than their deep-fryer.
Unless your water comes from a private spring, you should also filter your water. Town/city water has been rendered sufficiently sanitary from bacteria, microbes, etc., but there are many complex chemicals, pharmaceuticals, etc. that can't be filtered or are not part of the sanitation process. As a result, they're in your drinking water. So filter it to get these things out, and as a consequence of removing these things and a majority of the chlorine your water will taste better. I use the Berkey Light
http://www.berkeyfilters.com/berkey-water-filters/berkey-light.html
You can buy cheaper replacement filters elsewhere online.
Lastly, the running itself. Again, I'm not a girl, but what seemed to work well for me to slim down was 8-mile progression runs, where I go from slower than marathon pace to about 5k pace across the run. I use the first 2 miles to speed up to about marathon pace, remain at that pace as a steady state for 4 miles, and use the last 2 to progressively get faster and faster, and just churn out what pace I can on that day. I'm not a coach, so I don't know if this is optimal for developing certain bodily systems for a specific distance, but it was the "game-changer" that helped me slim down.
I wish you the best of luck. Don't body-shame yourself, don't worry about weight. Just eat right and run right, and you'll naturally slim down and be the best you can be.