Alana is very pretty. From what I've read from your post, it sounds like you are pronouncing the ending ANN-a (like Anna) rather than AH-na. Either pronunciation is pretty, but I think Alanna would be less likely to be mispronounced. I definitely think it could be used to honor your great-grandma especially with the spelling Alanna.
Out of your combos, I like these the best:
Alana Bridget
Alana Vivian
Alana July - I rarely see July used as a name. It would be nice to see it actually used.
Alana and Vivian make nice sister names, but I think they sound great as a FN/MN combo as well.
Other names you might like:
Ariadne
Calantha
Calandra
Vianne
Adelia
Adina
Adara
Adrienne
Arabella
Arabelle
Isadora
Amity
Alaia
Alastriona
Alessandra
Alessia
Althea
Elodie
Elodia
Alodia
Amina
Amandine
Amara
Amira
Annora
Acantha
Acacia
Aurora
Anthea
Artemis
Ambrosia
Elspeth
Cassia