Completely missed your first post. So here it goes:
Personally: I never give a free ticket to anyone (sorry...

), but if I can’t go I’d sell my ticket for face value. Since I always give everybody the benefit of the doubt, I’d initially sell to anybody. If I learn through the fan community of the respective artist that a certain person is ‘bad news’ (stalking behaviour, a scalper, etc) then I’d think twice about it and probably not sell to that person.
With the social media and all, it’s fairly simple to ‘get to know’ people. But before meeting people in private I’ve always had lengthy e-mail and/or phone contact with them. I’ve travelled to the USA (from Holland) to stay with people I’ve only met online. Of course we had evening-long chats and e-mail conversations, but still: it was a bit of a gamble. I did that twice and was never disappointed: I made life-long friends.
If you’re a fan of a certain artist, it’s not strange to uphold the same standards as that artist. So besides the music, you often also share some values with each other, which makes it easier to trust them.
But my advice is: check out their private profiles online (it says a lot if you see family pictures or pub pictures, if you get my drift) and always (!!!) have contact outside the social media before meeting people in private (especially abroad). Again: it’s a gamble, but in my situation both times it paid off real well :-) And let friends (and/or family) know where you’re going, give them address details, phone numbers et cetera. Never travel abroad to stay with people without having their address. Don’t accept a ‘I’ll pick you up from the airport / bus station / … and then we’ll just go to my place.’ Know where that place is (and streetview on google maps can sometimes be helpful).
I know I want to meet Susan once, as we already ended up standing next to each other during one gig, without knowing it (we figured it out afterwards).
Good enough advice?