All I have to say is wow..
I worked with someone that's due in August with her first. She was actually mad because her younger sister who is 2 weeks further along than her decided to tell the family she was pregnant with her 3rd about 2-3 days later.
The girl I worked with felt like her sister had "stolen her thunder" and had done it on purpose or was faking.. (timing of telling family, not getting pregnant obviously haha) Even after I tried pointing out that her sister had suffered through a m/c a while before this and that she should be happy her sister was pregnant again and they could at least compare notes on their pregnancies, she still seemed to harbour this anger towards her sister..
I've just never understood that, or the name thing. .. I get it if she was your sister and the two of you were super close and you wanted to use the same first name as one of her children and didn't even bother asking if it would bug her.. but it's a middle name.. She should feel honoured by what you're doing.
How does she even function in society? Does she ask strangers on the street to change if they're wearing the same outfit or have the same hairstyle as her?
I think you sent back a very mature response..I think I would have blown up and sent back something quite nasty..Or told her I'd changed my mind and that I was now going to name my daughter the exact same name as she has for her daughter.
That's partially why we kept the name for our son a secret. But mainly because it was very unique and we knew a lot of people wouldn't "like it". We figured if we waited till he was born, then people wouldn't be trying to convince us to change the name, and a lot of them grew to like it haha.
Hopefully she leaves you alone. And on the plus side, just look at her as adding some entertainment and a good laugh to your life with how ridiculous she's being.