The 1970's for women was a time of liberation, which included fashion. Some trends in the 1970's for women included mini skirts, bell bottoms, polyester blouses and many other types of clothing pieces were apparent in the 70's; however, the disco era is probably the most iconic part of the 70's. Therefore, creating a 70's costume for women should be drawn from the inspiration of the disco era.
Creating a 70's costume for women.
Pick a hair style that was popularized in the 1970's. A couple examples include the mullet or the feathered look made popular by Farah Faucet.