This name is also used in the (former Soviet) country of Georgia, where it is written as მილენა.If you go to Facebook and perform a search using the keywords "Milena" + "Tbilisi" or simply "მილენა", you will be able to find Georgian bearers. Be sure not to search for just "Milena", because then you will be overwhelmed with bearers from other countries.
This name is originally a Slavic name only not Italian or Spanish, however in the 20th century a Czech actress became very popular in Italy and the name Milena spread.
https://www.beliebte-vornamen.de/11675-milena.htm
https://www.behindthename.com/name/milena/top/germany-berlin
https://de.m.wikipedia.org/wiki/Milena_(Vorname)
https://de.m.wiktionary.org/wiki/Milena
https://de.m.wikipedia.org/wiki/Milena_Karas
https://de.m.wikipedia.org/wiki/Milena_Drei%C3%9Fig
https://de.m.wikipedia.org/wiki/Milena_Baisch