Whos right? Me or her....

It would not bother me either. It's not a contest , so don't let it become the subject of a fight. One of my close friends is getting married 2 months before me when I got engaged first and it does not bother me at all. I am extremely happy for her. My sister is getting married weeks after me...still no problem...happy for her too! Everyone picks their date based on when it is best for them...and some like a certain time of the year. Try not to think of everything having a 'motive'...just enjoy the planning process together. It's a lot of fun having close friends and family going through the same 'wedding stuff', sharing ideas, and shopping around. Instead of looking at it as a possible dividing experience...look at it as a possible bonding experience. This is a very happy time in both of your lives...embrace it and don't worry.

ETA: and when those stressful times come around, you will be happy that you have someone who going through the same stuff!