Spelling is most likely Smilja (smeelya, the lj is a diphthong which sounds like the ill in the word million)Also Mildred would not be a Croatian name, but many named Milka or Mila became Mildred in the US.
Interesting there is a record for a Smilja PUPOVAC (poopohvats) age 11 arr in 1920 w/mother Milica age 40 destination to Battle Creek Mich to father/husband NickThere is a notation on the ship manifest that indicates Smilja filed her "first papers" for Citizenship in 1937 They were both coming from and born in Oravac, Servia (which is an error! it is and has been in Croatia) Oravac is in Croatia, Lika region.They identified their Race as Servian.Could this be your POPOVIC?Perhaps the name was mis-spelled on the manifest?
Oravac is the name Selo simply means village and while some places have Selo in the name Oravac does not.
POPOVIC is derived from the word pop or priest the IC ending is a diminutive meaning son of, literally translated son of a priest.POPOVIC is found in many Slavic speaking countries.