Doing some squats and lunges will keep your behind round and nice. Also, Pilates is a good exercise to keep you curvy (I do Pilates every other day).
But also, when you are running, you are losing massive amounts of body fat. So, it's a good idea to up your caloric intake, if you want to keep your girly figure (I have curves also and don't want to lose them either by my running/jogging). Also, maybe, just run every other day (I do, 4 days a week) and on your non-running days do Pilates, lunges, squat, pushups (helps to boost the bustline too. No kidding!), and other calisthenics. And some weight training is essential too (at least 2-3 times a week).