Her color is Black Magpie
She is 100% most definitely not an English Spot/Flemish Giant cross. I don't see any feature of either of those breeds in her (flemish crosses usually have large ears, long fur and thick bone, english spot spot crosses are usually slender and tall). Neither of those breeds have the genetics to make that color: you need the chinchilla gene and harlequin gene to make magpie. English spots don't have the chinchilla OR harlequin gene and flemish giants don't have the harlequin gene. Even if we're saying that some Magpie colored rabbit was bred to an English Spot/Flemish it would take multiple generations to get back to this color as those genes are recessive. I just don't see how this rabbit could be either English Spot or Flemish cross, and I don't know where the rescue even got that breed mix. They often just call anything relatively large a Flemish and anything with white/black pattern an English spot.
In reality, this rabbit is probably a mixed breed, but if you had to put a breed label on it (for pet insurance or whatever) it looks closest to the breed "Harlequin" (Harlequins are a relatively rare meat breed that doesn't really end up in the pet trade often so it's unlikely to be a purebred Harlequin as well.)