Clementine is becoming trendy, and pales in comparison to the family ties that Doris has. Alma Doris does sound a little out-dated, though. Alma Lily has a youthful, lovely flow. It also means "soulful lily" or "white lily" together.
I do really like honoring family members in names though, but many of us think we have to use the actual name to honor. Doris has connotations to the water, and there are a lot of names that do too, like Ondine, Tallulah, Moselle, Oceana, Dorine, Dorissa, Cordelia, Marina, Marissa, and Nerissa. That way, they could still honor your grandmother, but in a new, fresh way that she can make her own.