Magdalena is a Biblical name. Usually shorten to
Magda or Magi. Sometimes, the French form Madlen/Madlena (
Madeleine) is used.
Miglena and Meglena is the same name with different spelling. I do not think it is connected to
Magdalena.
There are claims that Meglena comes from an old Slavonic word meaning "wind".
Most probably, the name Meglena came from a placename (toponym) Meglen and a river name Meglenitsa near the town of Edessa:
http://en.wikipedia.org/wiki/Edessa,_Greece
Most probably, the placename Meglen and the river name Meglenitsa come from Slavic mugla meaning "mist".