We are inviting my fiance's step sister to the wedding, but I feel like she has no proper etiquette!
A family friend had invited said step sister to her wedding a couple weeks back and gave her a +1 on the invite. This step sister has been dating the same person for over a year and instead, chose to bring her grandmother to this wedding as her guest, she informed the bride and we all thought it was a little odd, but it was whatever. The wedding comes around and this step sister shows up with a friend that no one had ever met!!! I was astounded that she thought this was acceptable! How can I avoid this happening at my wedding!? My fiance and I are not too close to her, so I think asking her flat out would be awkward. Thanks!