I did not think Bluebelle was being nasty. She was maybe a bit sharp but, that is all.
Bear in mind that, without body language and voice inflexions, what comes across in writing might have a completely different timbre if the person could be seen and heard.
I read your post twice because the first time it felt that you were being critical of your DiL and wanted to make her change her mind. When I reread it, I realised that all you were asking was whether anyone else found the choice of GC’s names stressful.
All I would say is, as I have already said, that children grow into their names or we get used to them. No need to feel stressed. Enjoy your new family member when he/she comes.