If you added the haha because you're thinking of the drink, it is an actual name, esp in Eastern Europe (it's the Latin version of Margaret), according to a quick google search.
As for her dad, I currently theorise for him to be either Ian (the war hero/person who knew Isabella/MC's previous self), or it could potentially be another high-ranking noble. The recent nightmare is suspicious, it very well could be that Isabella was raped, and she doesn't remember because of the body change.
I know there are probably people out there named margarita. Still funny for me though
Probably the green hair man, father and daughter revenge!
So who's Rita's dad?? Also is her name reslly margarita or its just the translation haha