I made a mistake and announced that I was pregnant at my sister's wedding.
What happened after the wedding?
I just felt really bad that I stole the attention from her on her big day.
Weddings are special occasions and it is not good to take away attention from the bride. It will make everybody upset and people will talk badly about you. It would be better to recognize what you did and apologize.
Well I'm busy next year, if you can I'll send a fb message to apologize.
You may be better off apologizing in person or calling her. Just explain to her that it was a mistake and that you feel bad for taking away her spotlight. Hopefully she is able to forgive you for doing this to her.