Ingrid and Claudia go well together - they feel cold and aristocratic. Daphne's just as posh, but much warmer. They all have contentious sounds - Ingrid is gritty, Claudia has the dreaded "clod" sound, many people think Daphne sounds silly. So we don't want a name that's almost self-consciously silky and smooth, like Julia. Claudia and Daphne are very posh and WASPish, so since we don't want two British names and two cosmopolitan names, we'll have to eliminate the likes of Astrid. And since we don't want the set to sound glum, we have to eliminate names like the mournful Opal.
Ingrid, Claudia, Daphne, and...
Adele
Alexandra
Annora
Athena
Beatrice
Beatrix
Beryl
Cornelia
Elisabeth
Elsa
Georgina
Henrietta
Irene
Minerva
Rosamund
Sophia
Susanna
Vera
Alexander
Benedict
Cedric
Conrad
Cosmo
Elias
Francis
Frederick
Hugo
Jasper
John
Julian
Julius
Leopold
Maximilian
Otto
Percival
Roman
Sebastian
Sylvester
Thaddeus
Theodore
Theophilus
Titus
Tobias
Victor
Virgil
masculine list:
https://www.behindthename.com/pnl/191050/124079feminine list:
https://www.behindthename.com/pnl/191050/124080