Milla is used as a pet form for many feminine names such as Camilla or Millicent. The 'Mila' element of the name is usually of Latin origin and meaning something along the lines of 'Pleasant'.
Milena (Cyrillic: Милена, Serbian pronunciation: [mÇlena], Bulgarian pronunciation: [mi'lÉ›na]) is a popular female given name of Slavic origin derived from word "mil" meaning "gracious", "pleasant" or "dear". It is the feminine form of the male names Milan and Milen.