I love
Elise so much. I've loved her for years and years!
1) Yes. It sounds like the tradition in your family is using forms of
Elizabeth as opposed to repeating the exact name of a previous generation. So
Elise would work perfectly for that.
2)
Elise
3) Still
Elise.
4) Not filler-ish. Would you consider
Lise? It seems less common and therefore less filler-ish...
Melody Elise actually flows quite nicely.