Amariah:
http://www.hebrewletters.com/item.cfm?itemid=5768
You are right, "is" is no feminine form in Hebrew. It could be a Greek feminine form of Amaryah though.
Amaris could be the Yiddish form of Amarit (
http://www.hebrewletters.com/item.cfm?itemid=7051), like Yehudis is
Yehudit's. Or it could be this:
http://www.hebrewletters.com/item.cfm?itemid=742 - although I'm not convinced by the (lack) of informations...
I hope it helps!
Claire