Sylvie Jne is my personal favorite!
Greta and Elsa.
Interestingly enough, we had Sylvie in our top 3 for baby girl number 3. I adore the name Sylvie! My husband felt it was too French sounding for our family (which I didn't really agree with), and I felt it was a little tongue twisty next to Elsa. I practiced saying the names together and didn't like it.....something about the repeated el and yl sounds (and then the s sounds being opposite -- els and syl) threw me off. Part of me regrets not using Sylvie, though. I think it is so sweet!
I like Olive with Elsa, since they're both short and start with a vowel; it compliments them.
Olive Helen is strong, and goes very well with Elsa Beatrice.
Sylvie also goes good with Elsa,as they both have that "s" sound, and Sylvie is quirky and short without the "a" at the end. Sylvia is stuffy and would have been too matchy with both ending in "a". Jane is kind of out of left-field, especially since Elsa has such a feminine, strong middle name of Beatrice.
And Alice is very close to Elsa. They don't look alike, but I've had that sort of problem. My name is Olivia, and while working with a Lydia, I discovered just how close those names really are when said in a hurry. Over the phone I get mistaken for Lydia or Elizabeth a lot... I guess when you say the names fast they sound kind of close!
Greta and Elsa sound good together too but... It almost sounds like Hansel and Gretal!
Thanks for the responses everyone! I like Greta, but maybe not with Elsa for our family. One thing I like about Elsa is that it has an almost international feeling. The name to me could be German, Spanish, Swiss... Our last name is Swiss and my tastes are wanting to skew more French with Sylvie (or Vivian maybe) whereas an Elsa/Greta pair (or Ingrid, which I also love) makes Elsa feel more German than it did on its own. Not sure if that makes sense...
Elsa was my husband's first choice from the moment I suggested it as a possibility and I actually had to warm up to it! I kept worrying she was Iris, even a day or two after she arrived! I love the name now of course. Husband's not sold on Sylvie, but maybe I'll get first pick next time around. :)