I adore the beautiful, very elegant Dahlia but pp are right - because it isn't used that often, the pronunciation will vary between "Day -lee- ah", "Dah- lee -ah", "Dayl -yuh", and "Dahl-yuh". Only you know whether this will annoy you (and potentially your DD).
Rose is the safe option - simple, classic, pretty, everyone knows how to say and spell it. Depends on whether you want a name that stands out (in good way imo) or blends in more?