Maybe you could name her
Elizabeth Roma and call her
Ella since people use
Ellie as a nickname for
Elizabeth anyways.
Eliza is also a nice nickname for
Elizabeth. I don't really care for the name
Roma, but if you like it a lot and really want to honor your great grandmother, it would work well as a middle name. Or maybe you could give her one name that has a special meaning for you and another that you simply just really like (i.e. a first name that you happen to just like quite a bit and then the name with the family connection or other special meaning as the middle name - or vice versa). You could also give her two middle names (ex.
Ella Juliet Rose,
Elizabeth Juliet Rose,
Ciara Elizabeth Jane, etc.)
other opinions-
Catalina -
Catalina is a nice name but it is fairly close to your name
Juliet - pretty but I prefer the spelling
JulietteCiara - very pretty
Arabella - pretty
Helena - pretty