Oh, okay. Sorry, I'm not familiar with either series. I sound kind of silly for discussing series I don't know about, especially when it comes to Bernkastel because they look so similar in both series and have deliberate connections with Rika such as the name FURUDERIKA-Bernkastel = Frederica Bernkastel.
But in Umineko Bernkastel's wiki, I noticed that it said in the trivia section, "It has been stated in an interview that she is the personality of the 100-year-old witch Rika seperated herself from in Saikoroshi-hen and is the crystallization of only the cruelest parts left over from the 100-year-old witch," and, "Her full name is heavily implied to be Fredrica Bernkastel due to Erika's duct tape seals reading, "E. Furudo Fredrica Bernkastel" in the PS3 version." (plus the screenshot) I wonder if those two facts are why Frederica Bernkastel is being used for the Umineko character - that the Higurashi character Frederica Bernkastel is the same as the Umineko Bernkastel.
Again, I apologize for my lack of familiarity with both series. I'm only going by facts that the wikis are saying and nothing more. If I could see the interview in question, it may make things clearer for me, and I can hunt around on YouTube for the PS3 part.