Little sister calls "dibs"

Stacey • Mommy to a 1 year old🎀. Expecting #2 in January!
My younger sister called dibs on the name ilah for a little girl. My husband and I have settled on the name Irah for our boy due in January. We picked the name together before we even heard about my sisters "dibs".
My sister isn't close to having kids, she just moved in with her boyfriend and they are no where near getting married let alone having kids (not that it needs to happen in that order). 
We told her our name, and she said that we can't use it, that it's way to close to her name..Is it wrong of me to be annoyed!?