I am not doubting you in anyway but this sound like a friction; how do you think of a woman contacting you without having a business deal before or even being link to someone that already established. You and I knows how it's for you or anyone else here to send you money or bitcoin without an escrow.
Yeah I had to read it twice and it did felt more like a fiction and if I'm not wrong, the 50k should also be in my own local currency, hence you should be from Nigeria but I think OP should also know that things don't work that way and no one just contacts anyone to make purchases online without having any personal connection or links or even referrals from reputable persons.
It also seems the buyer has some good knowledge of scam and how it works and there is no way she would want to risk her money just to prove a point without knowing you or having any connections with you.
So op you have to be very conscious and very careful of yourself.