I might have a few 3 syllables in here but with big sisters names, maybe:
[name_f]Aubrey[/name_f] (#130 in the USA)
[name_f]Brielle[/name_f] (#140 in the USA)
[name_f]Callie[/name_f] (#176 in the USA)
[name_f]Irene[/name_f] (outside the top 500) I personally think this one fits best with the sibset vibe.
[name_f]Ingrid[/name_f] (outside the top 500) this is my second favorite
[name_f]Ivette[/name_f] (not listed) debated typing this one down but even though it’s rarer, I find it a lovely complement to the set and not too hard on your other criteria.
[name_f]Miriam[/name_f] (3 syllables, sorry)
[name_f]Tessa[/name_f] (#303 in the USA)
[name_f]Marnie[/name_f] (unranked)
Hopefully these help 