monster in law getting married

Ok so maybe it's just me holding grudges...Sooo my sister in law  and I don't get along that much, when I go over to her mom's house while she's there she try's to tell me to clean, wash dishes, sweep, and cook, in the beginning I kind of did it because I was new to the family and didn't want to cause problems, but now I refuse to do it, I only pick up the mess that me and my husband make , she gets so bossy about it and tells my husband to tell me to clean.... anyways we don't get along, so out of no we're she messaged me this morning telling me she's getting married in 4 days and she wants me to go, she lives 3 and a half hours away , she expects me to go to her wedding , drive 3 hours there and drive three hours back, ( it is also the day after my 21st birthday... so that probably means I'm going to be hungover a bit) I also have school classes going on that day and marriage classes ( marriage classes for the church I go to... they are for in preparation for me to get married theough the church, because my husband and I are only married through the court and we want to get married through the church).. I'm getting married through the church in 5 months☺️. Anyways the last time I heard from her she had broken up with her now fiancé and started living with another guy, it's a surprise to me and my husband she even got back together with the guy she's marrying.. the guy is nice but she is mean and bossy! So my question is what should I do, should I go to the wedding, ( she's just getting married through court)( oh and also my husband isn't going because he's currently deployed )