Your poor friend must be really devastated to have been so hoodwinked by this guy. I think that you are right highlighting the general problems that arise about getting involved with any man - at least in this country there are ways and means of checking someone out and also gut feelings work within your own culture.
I think there are several ways of sussing out whether someone is not what they seem the first being to find out where they want to live. My guy is adamant that he doesn't want to leave Turkey - quite a good sign. He has also told me one or two of the tricks the workers in bars/restaurants etc use to a) get a shag and b)ensure you use their business. This is generally endorsed by their bosses.
One of their ploys is as you arrive maybe a group of four girls each will be singled out as special by one of the guys. They'll then woo the girl/s to their heart's content to part you from your spending money and get a bit of the other!! This will be the pattern for the length of the holiday - they'll even introduce you to people as "my girlfriend from England" or sometimes they'll imply that marriage is on the cards so the other people spend maybe more on drinks for the "happy couple" etc
The other little scam is to hone in on either the older one in the group or possibly the least attractive and make her feel very special. I've had this done to me when out with my daughters. I let them try their hardest for a while then explain a) I can understand what they're saying in Turkish to their mates and

I know how the system works and c) my guy will be along for a chat later!!
Don't ever leave a place with the promise from the staff that you can pay tomorrow - that ensures you go back!! And don't let anyone make you feel guilty because you're not eating/drinking at their place and "they've been so good to you......"etc
I think being aware of these 2 scams will help us women play them at their own game.
But I do want to emphasise that a lot of women misunderstand the attention given - not your friend particularly. I think she's learnt to read the signs now. Will she ever venture back to Turkey poor girl? I wouldn't blame her if she didn't but I think she should just for her own self esteem.