My husband liked [name]Sienna[/name] for our girl, and I wanted [name]Brielle[/name]. We combined them to make [name]Brienna[/name], which I think is really cute, but I’m afraid everyone will call her [name]Brianna[/name] by mistake. [name]Will[/name] it work, or no?
I could see that happening. I’d like to be optimistic and say no one would make that mistake, but there are people like that. My parents, for example, butcher the name of everyone they meet, even simple names like [name]Jana[/name] ([name]Jenna[/name]) or [name]Amy[/name] ([name]Annie[/name]). Maybe you’d like [name]Brenna[/name], although I could see people mistaking that for [name]Brenda[/name]. Maybe it’s true of any name?
At first glance I read it as [name]Brenna[/name]. Then it looked like you got creative with the spelling of [name]Brianna[/name]
People may mess it up! I know a [name]Brianna[/name] who prefers the pronunciation [name]Bri[/name]-[name]ANNE[/name]-ah and she gets [name]Bri[/name]-Ahn-ah a lot so I think that [name]Brienna[/name] in it self may get people pronouncing it incorrectly. [name]Sienna[/name] [name]Brielle[/name] would be a really beautiful name! 
I kind of like Brienne better, not totally sure why. For some reason i feel like it might be slightly less likely to come across as [name]Brianne[/name], if you’re hoping to avoid too much of that.
I actually prefer Brienne over [name]Brianne[/name]. It could be confusing for people though, but that could be a problem with a lot of names anyway. [name]Do[/name] what you like.
Brienne is also a character in [name]George[/name] R. R. [name]Martin[/name]'s novels A Song of Ice and [name]Fire[/name] and the HBO tv show Game of Throwns. She is a really butchy/manly knight. [name]Just[/name] keep in mind that people might make that association since the tv show and books are so popular!
My sister’s name is [name]Brenna[/name] (which I love and think is a beautiful and unique name) but no one ever gets it right when they read it. She gets [name]Brianna[/name], [name]Brenda[/name], Brienne, [name]Breeanne[/name]. It’s like people forget how to sound things out. Drives her bananas. Given her 28 years of frustration, I think it’s probably a safe bet people probably won’t grasp the nuance between “[name]Brienna[/name]” and “[name]Brianna[/name]” without constant correction, although I do love the name.