The only time that it is ok to wear someone else's headpiece is if you truly love the headpiece that is being offered to you, and you would have chosen it for yourself in the first place. You most likely would not even think of using a borrowed gown even if the fit were perfect. For some uncanny reason, the bride often considers the headpiece as an afterthought or unimportant trinket. It should be considered one of the most important elements of your ensemble. After all, it is near your face and hair. It's purpose is to bring forth the bridal glow in your hair and face. Everyone's attention will be drawn to you from head to toe. However, it is in your face that radiates your happiness on your wedding day. Your headpiece should be a very personal decision and it should be chosen with the utmost of care. Therefore, if it is your "borrowed," it might not be the perfect size, style, or fit for your hair and face.
Go to http://www.maryclarydesign.etsy.com/, and for a very reasonable price, you can have the perfect headpiece for you.