Congratulations on her imminent arrival! So exciting! : D. You have great taste! Here are my thoughts and some suggestions:
[name]Nina[/name] - a beautiful name that is universal in appeal. A [name]Nina[/name] could have a sister with just about any name. If she changes her name when she marries [name]Nina[/name] will go with anything. It will go with nearly any middle. It will go well with your surname. A wonderful name.
[name]Edith[/name] - a really cute and appealing name (love [name]Edie[/name]) that feels very Old English and will mesh well with some of this list better than others. [name]Edith[/name] and [name]Irene[/name], [name]Edith[/name] and [name]Vera[/name], [name]Edith[/name] and [name]Vivian[/name], [name]Edith[/name] and [name]Cecilia[/name] all feel like sisters…others maybe less so.
[name]Cecilia[/name] - a classic that will go versatilely with most of the others on this list if you have future daughters. Cici is a cute nn. [name]Silke[/name] if you want to acknowledge the [name]German[/name] heritage that way is another awesome nn.
[name]Esme[/name] - I like this but not as much as most of your others and it feels a lot more modern and French than much of this list. I’d use it if it’s your favorite but otherwise I’d put it away.
[name]Helena[/name] - a wonderful classic with lots of nn options that pairs very well with [name]Cecilia[/name] and [name]Vera[/name] on this list. [name]One[/name] of my favorite names.
[name]Irene[/name] - I have a bad association with this name, so, I should step out. But it feels more old ladyish than the rest - I’d put it with [name]Esme[/name], unless it’s your favorite, pick something else.
[name]Ingrid[/name] - I like [name]Ingrid[/name] and it’s a great name for a [name]German[/name] girl. I don’t know how well it pairs with much of the rest of your taste though if you care about that for future daughters.
[name]Elisabeth[/name] - Can’t go wrong. Classic and so many nicknames. [name]Do[/name] wonder if your last name is long if this is a bit of a mouthful of a name, but it’s still so classic it works.
[name]Vera[/name] - one of my very favorite names ever. I always root for it!
[name]Vivian[/name] - another great name. I do feel like it’s having a bit of a sharp rise right now that might be followed by a sharp fall? [name]Just[/name] worth thinking about it. Still love it
[name]Oona[/name] - I have such a softspot for this name, but I think it is hard to pull off / pair with a more mainstream sister. I think it works by a stretch as a nn for [name]Johanna[/name] (someone once told me they knew an Oana nn for [name]Johanna[/name], and then [name]Oona[/name]'s just one more letter), if you like [name]Johanna[/name].
Suggestions:
[name]Margaret[/name] family + [name]Ingrid[/name] = [name]Greta[/name]? [name]Gretchen[/name]?
[name]Irene[/name] + [name]Agnes[/name] = [name]Iris[/name]?
[name]Lucy[/name]/[name]Louisa[/name] + [name]Oona[/name] = [name]Luna[/name]?
[name]Josephine[/name] + [name]Rosemary[/name] = [name]Rosalie[/name]?
[name]Helena[/name] + [name]Esme[/name] = [name]Elena[/name]?
[name]Agnes[/name] + Ingred = [name]Ines[/name]?
[name]Cecilia[/name] + [name]Rosemary[/name] = [name]Cecily[/name]?
[name]Nina[/name] + [name]Oona[/name] = [name]Anona[/name]?
Good luck!