Chief bridesmaid or otherwise known as the matron of honor usually receives a more lavish gift than the other bridesmaids.
The matron of honour is normally responsible for organising the hen night and bridal shower. Consider spending a more on her for the extra mile that she goes for you.
Your matron of honour should have been there for you right from the announcement of your wedding day, she should have been your rock throughout all the stress and preparations including going with you for your wedding dress fittings and attendance at any wedding rehersals.