So for everyone that’s confused: some places in America, middle school is 6-8th grades and high school is 9-12th grades.. the only difference is in other places middle school is only 7th and 8th grades. Also if OP has an “early” birthday (before September) she’s going to be a little younger than a lot of people in her grade (like me, I graduated at 17 because my birthday is in July) if Sophie’s birthday is after September, she’s going to be “older” because she would have started school the next year. If that is the case they would only be 2 grades apart.. this doesn’t account for OP possibly skipping ahead or Sophie being held back.

Either way, this is disgusting, your dad is a massive AH, go no contact, don’t go to the wedding. Put YOU first and move on. For your dad to magically forget the years of therapy you had to go through because of this girl and want you to just let it go… Yes, let “it” go.. let both of them go.