Allegra is well-known among Afrikaans-speaking South Africans, though not widely used. Probably the software company will kill it off for human use.
I've encountered older women named
Dulcie, but never Dulcina.
Dulcie is too lightweight and nicknamey, but Dulcina seems to be trying too hard.
Davina doesn't appeal to me, though I love
David and used it as my son's mn. Sounds like an unsuccessful variant of Divine.