You and your sister were pregnant at the same time, but she’s like 3 months ahead of you, and you tell her what you want to name your baby, and she steals the name and name her own baby the name you picked?
Well, I being male could never get pregnant for starters.
But if I was a female and that was the case that you listed, hopefully the middle name would be different, and I hope to God the father's last name is different as well. And I would name my child as I wanted too anyways.
I'd be pissed off. My aunt actually gave her daughter the same name I have. She's 9 years younger but every time someone mentions the name in the broader family they have to specify which of us they mean. So yeah, it'll be a mess.
That's exactly what happened to my cousin in early 1993, she came up with a very unique name for her son while she was pregnant with him, she made the mistake of telling her friends, one who was about a month closer to delivery than her, when her son was born she stole the name my cousin came up with for her son. It cost a friendship going back to kindergarden in the mid 70's.