I'm trying to loose about 30lbs. if i combine my diet with a workout, will i become thinner or bulk up? thin is the goal. what exercises are useful?

Unlikely: To significantly "bulk up". Women have less potential to gain "bulk" due to different hormones levels then men. You may gain some muscle mass, if you start doing resistance training and have never done this ever before. But you will likely start losing some fat mass too. Seek the input of a personal trainer for a reasonable exercise plan, as it's difficult to answer in this limited space.

Do aerobic exercise: Aerobic exercises, like running, swimming & elliptical machines, will burn calories and lead to weight loss with little additional bulk.

Depends on exercise: Typically with exercise of the cardiovascular type, you don't bulk up as much as if you were heavy weight lifting. As you work the heart and lung with whole body movements but use low weight training, it can help the body regulate size and use big muscles for fat burning capacity. If you lift heavier weights, the size of the muscle increases and can bulk the body.