I can't find anything in Barcy, France (north-east of Paris). But there's a Burcy a little south of Paris and a Bussy, all three are still in Marne-et-Seine. I also found a Burcy in Normandie...which is another possibility, because that is much closer to the coast and England.
How long would it take to get from Paris to the coast if you were escaping and hiding? It's roughly 100 miles. The pioneers walked on average of 10 miles a day. That would make it about 10 days from Paris to Le Havre. One to cross the channel and then how to get from southern England to Liverpool? And why would her brother and sister die? Was it winter? Did they travel at night? If it was a local dispute, once they were a couple days away from the area, it shouldn't have mattered. So if they were followed and George and Sylvia killed, then it must have been a bigger issue. Or maybe they died in the initial escape from their home, at the beginning of the event.
What about their parents? Their parents have never been mentioned. Were they killed outright? Were the children given instructions to leave if the parents were arrested? Were they orphans already?
We have no idea whether they were upper- or lower-class. I'd have to assume for something of this sort they must have been fairly well-to-do. It doesn't make sense that poor farmers would be chased out of the area. That would also make more sense if she truly was a "companion" to a wealthy woman--"Lady" Goodall. A poor farm-girl would not have had the training to be a companion in a wealthy social class. But it doesn't explain the "servant" occupation in the 1861 Census with Charles Taylor. That can only be explained as covering up for their relationship. I'd think that "servant" must have been accompanied by a wink and a knowing grin when the census-taker wrote it down.
So how did she escape anyway? And what exactly was she escaping from? Did she have help? Was there someone who took care of her or did she have to find her own way?
So, supposing Marian was hiding all the way across the channel. What next? Did she have any money to live on? Did she have any idea of a job? How did she get the job of being companion to Lady Goodall in the first place? Did she have the position promised to her before she left France? Did she have a safe place to go to in England? If she was well-to-do, were they able to bring anything with them? If as it says, she came as a young woman, [one document says sixteen] then what would she have done to make ends meet until she got the position as companion? I wonder if she was turned away from her position with Lady Goodall because of her interest in (or assignations with) Charles Taylor. It is easy to believe that in that position she met Charles Taylor and "changed jobs".
Okay, here's an awful thought...what if she wasn't companion to LADY Goodall but a Mr. Goodall? What if William is truly William Goodall? Don't know. Never thought of this possibility before and truly, I never would have dared write it down if all the closer relatives weren't already gone. But what if Mr. Goodall picked her up in France and brought her to England and then for some reason they split up and she found Charles Taylor? However, I don't think she would have left one safe position without expectation or knowledge of another. On the other hand, She had to have been of at least a middle-class social status or she couldn't possibly have retained Charles' interest long enough for the births of all their children...although I am leaning to the belief that Alice Jane was the product of a last-ditch effort to retain his attention.