You couldn’t use Elizabeth with a different nn to your relative? There are so many.. or you could use a variation like Elsbeth which would give you Buffy, Effie, Essie, Ellie, Elsie, Betsy, Betty
Anna / Annalise / Annis - Annie or Nancy
Susannah - Sukey, Annie, Susie, Nancy
Lydia - Liddy
Eleanor/Helena - Ellie, Lenny, Nell, Lena
Dorothea/Dorothy - Dorrie, Dorey, Dottie, Dot, Dora, Thea
Margaret/Marguerite - Margo, Maggie, Peggy and (traditionally/weirdly) Daisy
Caroline - Callie
Marianne - Maisie, May, Polly, Molly, Nancy, Annie
Mary / Maria - May, Maisie, Polly, Molly, Minnie, Min
Marina - Marnie
Frances / Francesca - Frankie, Franca, Francie, Frannie, Chessie, Chesca
Victoria - Vicky, Tory, Vita (I also know a Plum)
Alexandra - Alecky, Sandie, Ally, Sacha, Andie
Stephanie - Stevie
Georgina - Georgie, Gigi
Henrietta - Harriet, Hetty, Hatty, Hennie, Harrie, Etta
Cordelia, Cordelia - Cordy,
Natalia - Tally, Natasha, Tasha, Sasha
Patricia - Pasha, Tish, Patchy