Completely unreasonable.
Just because you love that name does not mean she can't, just because you announced it does not mean she has to avoid it, just because she didn't announce it doesn't mean she was doing something wrong.
She picked the name she loved for her child, thats it... you have ZERO more rights to the name than her.
She has not stopped you naming your child or controlled what you do so you have no right to think she should have let you have input in her child's name. You could use the name you love but you CHOOSE not too, you cut your own nose off to spite your face not her.
Do people REALLY think anyone else names their kids with other people in mind? its between the parents only.
I choose my DS name as a kid, I loved it for 23 year and DH loved it too. I suffered 10 years of infertility, had a loss, did IVF... in that time TWO family members (one my side and one DH side) used my chosen name. Its not even a common name.
Was I mad? no, I had bigger shit to deal with on my own parenting journey.
Did I still use the name? yes, because that was MY child's name born or not and we had been using it to refer to our future child forever.
Has anyone ever given two shits that 3 family member have that name? nope, literally a complete non issue. Historically it was super common for families/cousins to share names, in many cultures it still is even among siblings.
I know if my family member had the audacity to confront me and claim I couldn't use my chosen name for MY child I would tell them very unpolitely exactly where to shove their unwanted opinion regardless of which of us gave birth or announced first.