Help on breaking the news to my sister

Since my husband and I have found out we were pregnant, like everyone else we started talking about potential names for our baby. We were so certain we were having a baby boy that we didn’t even focus on girl names. Our anatomy scan rolls around and we are shocked and absolutely thrilled to find out we are having a little girl. Picking a name for this little lady has been the most challenged thing for us. We’ve finally decided on one that we both love, a name that we feel is both beautiful and strong and will evolve with our daughter from infancy into adulthood. I shared the name with my family (my mom and two sisters) everyone loved it but my older sister mentioned that’s the name that her and her husband had picked for when they have a little girl. At first she told me that they had other names picked as well so it wouldn’t be a big deal if we used the name but after sharing the news with her husband and getting his reaction she has been more adamant about us not using it. I’ve tried my absolute hardest to be considerate of her feelings and I have searched every list trying to find another name that we thought could be perfect for our daughter but nothing has come close and we keep coming back to this name. Naming our daughter is not something we want to take lightly or something we feel we should compromise on. A name is a very important thing and to us it means something. I need help breaking the news to her that this is the name we’ve chosen. So far my family has been no help with the situation. My sister is know for her anger and attitude and her husband is an absolute nightmare so the family would rather not deal with their drama. So instead of comforting me during this situation I feel like they are trying to persuade me into choosing something different so my sister can have the name. Please help I’m not sure how to approach this topic with her.