On the day of her father's death she issued a statement as "Custodian". If you look back at some of the threads from that time IIRC there were even Romanian media sources claiming that she would be officially acknowledged as Queen by the government, albeit in their current quasi/semi official role not by a return to reigning. If she's given a style it's more often than not "Her Majesty Margareta COTC".
I do think it is impressive that they have carved out an agreement with the republican government to have a semi-official role. It is interesting to see that not only does she greet foreign ambassadors but holds official audiences with military brass and government officials.
It was not Maragreta's own choices but set up by her late father in his "Fundamental Rules for the Royal House of Romania"
About the title "Custodian of the Crown" :
1. My eldest daughter, The Princess
Margareta, is to be my successor and
Head of the Royal House of Romania,
after my death.
If the Romanian Nation
and Parliament were to decide to
reinstate the Monarchy as the form of
government, I ask the Parliament to cease
to implement the Salic-law as the form
of succession, which does not correspond
either to the elementary rights in Europe
today, or to the values of Romanian
society.
Until these events should come
about, The Princess Margareta will
remain, after my death, Head of the Royal
House of Romania and
Custodian of the
Romanian Crown.
About the style of "Her Majesty" :
2) The Head of the Royal House of Romania, by all common
practice and convention, is de jure or de facto Sovereign in
terms of their authority over the Royal House of Romania, at
any time.
Immediately upon the death of the Head of the Royal
House of Romania, without further proclamation, the Heir
Apparent or Heir Presumptive, whichever shall be living and
first in the line to the succession at that moment in time, shall
from that moment
assume the rank or style King or Queen,
regardless of the Family's position as a reigning or non-reigning
Dynasty and regardless of the fact that they may or may not
later choose against the use of such style or designation.
The Princess Margareta has assumed the traditional form of address for a Queen ("Her Majesty Margareta" or "Her Majesty The Custodian of the Romanian Crown") but omits the title of
Queen as long as the monarchy has not been reinstated.
