Ooh this is a tough one, because names are gorgeous[name_f][/name_f]. However I think stylistically, [name_f]Matilda[/name_f] is a better fit with the brother names. I’m answering this as a [name_m]Brit[/name_m] admittedly, and [name_m]Arthur[/name_m], [name_m]Hugo[/name_m] and [name_f]Matilda[/name_f] are very on trend here, so those names just go together for me.
[name_f][/name_f][name_f]Rosemary[/name_f] is fabulous, and does work with the brother names, but not as well as [name_f]Matilda[/name_f], imho.