I really love Teddy (even just on it's own) and Buffy is a cute nn for Elizabeth - I never thought of it myself tbh.
I haven't read through the whole thread, so sorry for repeats!!
Dorothy nn Dolly/Dollie or Dottie
Charlotte nn Lottie
Martha nn Maisie
Matilda nn Tillie
Harriet nn Hattie
Edith nn Edie
Beatrice nn Betsy, Bea or Bess
Florence nn Florrie, Flossie or Loren? (my only selling point for s/o is that a Florence could use Loren when she grows up if she thinks her name is too old-fashioned
)
Katherine/Catherine nn Kitty
Evelyn nn Evie
Lillian nn Lily/Lillie or Annie
Sybil nn Billie
Margaret nn Maisie, Maggie, or Greta
Rhiannon nn Annie
Daniella nn Ella, Ellie or Annie
Rosalie, Rosanna, Rosamund, Rosalind nn Rosie
Eleanor nn Nellie, Elsie, Ellie or Nora!
Tabitha nn Abbie/Abi
Alfred nn Alfie
Albert nn Albie or Bertie
James nn Jamie
Ernest nn Ernie
Henry nn Harry
Jacob nn Jake (biased bc s/o's name)
Wilfred/William nn Will/Billy
My favourites with Buffy and Teddy are Kitty, Lottie, Billie, Annie, Elsie, Betsy, Hattie and Dollie, and for boys, I love Ernie, Jamie and Jake.
hope this helped !