Oh, I’m so, so sorry to hear that your sister has chosen to use [name]Julia[/name], and I felt like I was kicked in the stomach when I read that she knew you had already chosen [name]Juliette[/name]. [name]Ouch[/name].
In my opinion, her decision to use [name]Julia[/name] speaks a lot about her character. You say she’s the [name]Golden[/name] Child, and it seems as though she’s gotten used to putting her desires above yours. I’d love to have a little chat with her. 
A poster named [name]Gracie[/name] once dealt with a similar issues, and I wrote that while we can’t control what other people do, we can control how we react to them. While you need to do what’s right for you (and while it may be easier said than done), I personally hope you’ll consider the source, shake it off, and stick to the gorgeous name you’ve chosen.
(Plus, if she chose [name]Julia[/name] while she knew you were going with [name]Juliette[/name], the similarity clearly isn’t an issue for her, so it’s not as though she has a right to get her panties in a bunch should you opt to keep [name]Juliette[/name].) 
While ideally it would it great if the first cousins had names that differed more, I vote that you stick with [name]Juliette[/name]. [name]Juliette[/name] and [name]Julia[/name] may live near each other at the moment, but one of you may move in future; also, the two cousins may not live anywhere near each other when they grow up, and I think it would be a shame to deny your daughter such a gorgeous name. (I absolutely love [name]Juliette[/name]!) 
If you’re too bothered to use [name]Juliette[/name], though, you may also like:
[name]Amelie[/name]
[name]Annabelle[/name]
[name]Camille[/name]
[name]Genevieve[/name]
[name]Josephine[/name]
[name]Mirabelle[/name]
[name]Rosalie[/name]
[name]Vivienne[/name]
Another option could be using [name]Juliette[/name] in the middle.
I hope everything works out for you! 
I’m sending hugs your way!
