Invitees To A Bridal Shower

Help!
My stepdaughter is getting married and her bridesmaids are throwing her a shower. The maid of honor informed me that they will be inviting all of the women who are on the wedding invitation list. I am uncomfortable with this since some of our guests do not know the bride well and others have never met her. I am concerned that they will feel obligated to come and/or send a gift.
Are there some general guidelines for who is invited to a bridal shower?
Thanks,
Leslie