They are all nice names, but they all sound very similar to Etta (great name by the way!) and if i was the child in question I'd like more individual identity in my name - not to be too similar to the sister's name.
If it was me I'd go for a different start letter as Ada so similar due to the vowel start, two syllables and same ending and Effie and Edie both really similar due to same start letter and two syllables. I think if I liked super short names I'd go for something with a consonent start. Like Maeve and Niamh maybe. If you're particularly liking older gen names like Effie (Euphemia) there are things like Mabel and Clara and Nora and Dora, Rosa, Lucy, Polly, Daisy, Iris etc. Or if it's the general sound and format you like perhaps a strong consonant at the start would differentiate them more. Mia (I know it's super popular) Maya or Fia or Freya are similar format but seem more differentiated. There's non-granny names that are shorter with two syllables and a on the end like Tara and Cara or Dinah and Gina etc. Not saying any of these are better, just that I feel I'd like a bit more of an individual name for myself if I was the child in question and not be too similar to my sibling's name.