Question: is there a difference between maid of honour and chief bridesmaid

Answer: No, The principal bridesmaid, if one is so designated, may be called the chief bridesmaid or maid of honor if she is unmarried, or the matron of honor if she is married. A junior bridesmaid is a girl who is clearly too young to be married, but who is included as an honorary bridesmaid. In the United States, typically only the maid/matron of honor and the best man are the official witnesses for the wedding license.