Personal names, since they refer to persons and personalities, have many `meanings': colored by the multitude of emotions that holders of that name, real and fictional, that they evoke in us. Many of these are intensely personal, some transcend to a cultural mileu, a few reach the linguistic domain. Every field of study has to draw a line somewhere: a study of names, as opposed to the study of people, or of history, draws it somewhere in the latter domains.
In this particular case, if Militza is ultimately derived from
Milica, most of the questions in the onomastic domain are answered by that entry.