The tradition of having lots of bridesmaids and groomsmen is changing! It is YOUR day, and you don't want anyone taking the attention away from you. Your bridesmaid(s) should be a friend or family member who has always been supportive and encouraging to you. You will want someone you can rely on in the event you forget something in your hotel room, or need a last-minute alteration to your dress!
While it is your special day, it is a good idea to take the feelings of your family into consideration when planning your event. But it is your day! A sister or cousin may be offended that you chose a friend to be your bridesmaid. Instead of calling her your bridesmaid, give her the title of "Personal Assistant." A true friend won't mind the name-change, and your family won't feel the sting.