conflicted

So My sister is 21 and her partner is 45. Mentally they are the same and everyone supports them. Except my mom, not because of the age but because my sisters partner is non binary meaning they do not identify as he nor she, and this is really frustrating to me. I'm only 14 but I believe that love is love and I am unsure what to say to my mom to make her understand there relationship and I just want to help my sister because she's going through a lot. My mom is not religious by any means. Can anyone give me any ideas for how to help my mom understand my sisters relationship.