Is it a must that I invite my brother’s longtime girlfriend to my wedding?

Is there a written rule that we must follow that requires partners of siblings to be invited to a wedding? Did you guys extend the invite to them? Hindi naman kami close nung girlfriend ng brother ko and the girlfriend has been rude to me and my mom on several occasions already. I’m afraid that the girlfriend will act entitled on my special day as there has already been many precedents — like how she acted so “paimportante” on my birthday celebration and yet never once talked to me nor thanked me for inviting her. And besides, the venue can only accommodate a limited number of people and sobrang hirap na kami ng fiance ko to trim down our guest list. Strictly no plus ones. I wanted pa nga sana to invite my favorite clients pero di na talaga kaya. Iniisip namin wala naman ambag sa life namin iyong girlfriend. Pero bakit ganun, bakit pinapamukha sa amin na kami iyong inggrata if we do not invite that person? Ano ang kinalaman ng pagiging better person sa pag hindi pag invite sa kanya?