I'm not so crazy about the same-letter thing myself, but if you insist:
Adena and
AlessandraElizabeth and
EveRhiannon and
RoseCatherine and
CassandraJulia and
JillianDaria and
DanaI myself would go for a theme:
Shakespearean:
Ophelia,
Juliet,
Miranda,
Cordelia,
Beatrice,
Portia,
Helena, Katherine(Katharina),
OliviaFlowers:
Rose,
Ivy, Violet(Viola), Lily(Lillian, Lillith),
Daisy....
Biblical:
Leah,
Rachel,
Sarah,
Rebecca,
Adah,
Ruth,
Naomi,
Zillah