[name_f]Bree[/name_f] feels really natural and I am definitely a nicknaming person. However, I will always ask if they prefer their full name or a nickname.
[name_f][/name_f]I know a [name_m]Joshua[/name_m] who hates being called [name_m]Josh[/name_m], and is always[name_f][/name_f] [name_m]Joshua[/name_m]. There is no exceptions haha.
[name_f][/name_f]I know a [name_f]Josephine[/name_f], [name_f]Isabella[/name_f], [name_m]Thomas[/name_m], [name_m]Tobias[/name_m], [name_m]Alexander[/name_m], etc. that all go by their full names, despite there being a very logical and common nickname.
[name_f]My[/name_f] point is that if you always introduce her as [name_f]Brielle[/name_f], people should get the gist. And if [name_f]Brielle[/name_f] only wants to be known as [name_f]Brielle[/name_f], she will be able to reinforce that herself as she gets older. I don’t think it would be a massive issue. It’s also only two syllables so people should adapt easily if corrected!