I understand how people say, "Oh my God, how could those girls be so foolish", but the honest truth is we trust people and when things happen so fast it is hard to pull back. You fight with your inner thoughts about what is true or not, but you find yourself being dragged in further and further.
Simon was really good, what you saw is not what was real, but it reality, it looked so real. Yes, I do agree that once you start dishing out thousands of dollars, the red flag should go up. Best thing is to call a friend, family and discuss the situation with them. Someone on the outside is not emotionally involved and is able to think straight and see things for what they are.
Easier to judge these girls when you know what the movie is about, but beware, con artist are everywhere, so be careful. Hopefully, this movie taught you a few things and you will question things when they look too good to be true, especially when things start falling apart fast.