Baby Naming with Bff

Well my bff and I did it! We managed to get preggers together. She's 3 weeks ahead of me, and found out that she's having a boy! She started looking at names, and I've been right there with her, cheering her on. My SO and I have been discussing name for over 18 months, (ever since we started trying) and we ended up at Sebastion Zachary a few months ago. Well, she has been tossing around Dylan, and trying to come up with a middle name and she settles on Zachary and announces so on fb. I am super supportive, and mention how cool it'll be that our boys (I'm being wishful) will share the same middle name. Well, she apparently forgot that I am using it, and now she's really mad. She wants me to change my selection, to which I would be more willing to do, except it is my brothers name, and it means a lot to my family that I'm using it. My thing is, it's a middle name and I think she should either be cool with us both using it or unfortunately think of something else. I just feel really bad that she got really excited and then got the rug pulled out from under her.