I know a Della but she's up there in age ... late 50's. So I don't know if your considering names more common for around when you were born or not.
Are you stuck on keeping your initials the same? If not what's wrong with your posting name or a form of it? Emma, Emily
Dannika could also be Danni.
Most popular baby names of the 70's that start with D.
Dawn, Danielle, Denise, Deborah and variants, Dana, Donna, Diana, Deanna, Dorothy, Darlene, Desiree, Deana, Darla, Dorcy, Darcy, Daphne (Scooby Doobie Doo), Dionne, Dora, Dolores, Doreen, Demetria, Deirdre (like Jennifer Boylan's SO), Daisy, Delia, Dayna, Danielle, Dixie, Destiny, Denise, Dee.
That's most of the top 1000. I searched google for "female names 70's" and then searched for names that started with D. If you want to see the complete list it's the second link. I spent around two months before deciding on a name and have yet to change it legally but settled on something that I like and it only flops around my first two initials.
Good luck,
Jamie