i don’t personally love the flow of [name_f]Anne[/name_f] [name_f]Fern[/name_f] (i find it a little choppy), but of course that’s no reason not to use it if it’s what you prefer 
[name_f][/name_f] i do really love [name_f]Annie[/name_f] [name_f]Fern[/name_f]! i don’t think it’s too much, as [name_f]Annie[/name_f] and [name_f]Fern[/name_f] are both definitely familiar enough imo to make it a good double-barrel. i think it works as both a double FN and a FN + MN, but here are some suggestions for middles…
[name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Beatrice[/name_f] / [name_f]Beatrix[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Cordelia[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Josephine[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Kerensa[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Linnea[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Louella[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Matilda[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Ramona[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Rosalie[/name_f] / [name_f]Rosalind[/name_f] / [name_f]Rosamund[/name_f] etc
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Theodora[/name_f] / [name_f]Theodosia[/name_f]
[name_f][/name_f][name_f]Annie[/name_f] [name_f]Fern[/name_f] [name_f]Winifred[/name_f]
