My mom says she isn't going to attend my wedding because she wants to sit with her boy instead of with me!

Your mom needs to get over it and realize it's YOUR day. NOT HERS. She needs to put her selfishness aside and consider that this wedding is not a plot to make her look stupid because she's there without a date. What WILL make her look stupid is if she shows up with some guy half her age, that nobody- including you- knows.... and when you're looking at your photos in a couple of months, you'll have to explain to people that he was the guy your mom was seeing at the time and isn't related to your family in any way.