Please don't try and seal her neck up again, it could cause future problems should you ever choose to part with her. It looks like either her neck was pulled apart at some point or someone half tried to remove her head at some point.
IMHO I think she is authentic, but that is only my opinion. You have to see how you feel about her.
It is tricky as we do not understand how she came about, no one has ever found one MOC or MIB so we do not know of her distribution, was she an end of line "lets make ponies using the left overs", was she some sort of "exclusive" and so on.
As I have said before, buying ponies is taking a risk you take and nirvana ponies are an even bigger risk.
Love pkw xxx