What is a good thing for a mature 17 year old girl to wear to a wedding?

I would suggest wearing a colored dress to a wedding, since weddings are formal and they have a theme of new beginnings and unity. You shouldn't wear neon colors or crazy patterned clothing because that takes away from the elegance of your outfit, even if you are wearing a dress and your accessories are formal. Simple and formal is always safe for a wedding. If you have a dress that you wore for prom or a school dance that is knee length or floor length and simple, you could wear that. If you do not have any dresses, you could look at JcPenny and Macys. They usually carry formal dresses for a lot of different occasions and their prices are not too expensive. Bridal shops also carry dresses that are appropriate for many ages and styles.