Help pick a middle name :)

[lilmizmombassa.livejournal.com]

My sister, knowledgeable about my name obsession, has asked me to give her some suggestions for the baby she and the hubs are TTC. Baby boy would be Frank William, after his dad and maternal grandfather, and the girl name is up in the air. My sis likes Ava, and her husband likes Isabella. Her husband likes Italian girl names. They don't want anything too weird, too nature-y and at this point don't care about the meaning. I know it's like the most vanilla question ever, but any names which would pair well with Isabella or Ava and fall into those guidelines? Any help is great....thanks! :)