I would upload the video privately, password etc and only show it to clients by email, you could even ask them not to share it. Your sister wouldn't know, and you won't tell her.
Did they ban cameras and mobile phone videos at the wedding?
Your sister and her partner (despite how lovely they looked on the day) are not George Clooney and Amal Alamuddin, no one gives a hoot to share their special day, except your family.

Has she seen the video? Heres a test : if you upload it privately and send it to her, and she posts it to facebook, theres your answer, she may be dazzled by your skills and want to show everyone how amazing she looked.

Clients are looking at your abilities not the nameless throng in their best.

If possible cut any children out of the video, thats a touchy subject for some.

1 year is enough free work, 2 at the absolute maximum in my opinion, you know your worth and others will too.