I would not get a bob in my opinion. If you have long hair right now, to have a short bob is way too drastic of a change and I'm afraid you'll regret it.I personally believe everyone should wear their hair whatever length and style they feel most comfortable wearing it.Some people feel just as mature in long hair as short. Ditto with feeling feminine.People with short hair can feel just as feminine as those with long hair.
If I were you, I would get my hair cut maybe an inch or two above the shoulder line. Then ask the hairdresser to frame your face, give you some long layers, and if you don't already have them, side-swoop bangs. This haircut looks great with almost all face shapes and hair colors. Long layers will make the ends of your hair more thinned out that way they wont curl in or out or look too thick. They will also keep you from getting split ends as fast. Framing your face will draws attention to your face and helps accent your natural features. It also helps blend in layers and bangs. I think side-swoop bangs are adorable. I have them and I think they look great. And after a little while of getting used this length, you can go shorter if you would like to.