She's being naive

In the last few sections of the play I didn’t find any humor in it what so ever. In fact these sections make me angry. I don’t understand how Shen Te can be so ignorant and blind even after she heard Yang Sun tell Mr. Shui Ta that he wasn’t really in it for the love, but for the money that she could give him for his pilot job in Peking. The conversation starts on page 55 when Yang Sun talks to Shui Ta to get him to pay up the rest of the money for him to go to Peking and become a pilot.

Shui Ta: Two people can’t travel for nothing.
Yang Sun (not giving Shui Ta a chance to answer): I’m leaving her behind. No millstone around my neck!
Shui Ta: Oh.
Yang Sun: Don’t look at me like that!
Shui Ta: How precisely is my cousin to live?
Yang Sun: Oh, you’ll think of something.
Shui Ta: A small request, Mr. Yang Sun. Leave the two hundred silver dollars here until you can show me two tickets for Peking.
Yang Sun: You learn to mind your own business, Mr. Shui Ta.
Shui Ta: I’m afraid Miss Shen Te may not wish to sell the shop when she discovers that…
Yang Sun: You don’t know women. She’ll want to. Even then.
Shui Ta (a slight outburst): She is a human being, sir! And not devoid of common sense!
Yang Sun: Shen Te is a woman: she is devoid of common sense. I only have to lay my hand on her shoulder, and church bells ring.
Shui Ta (with difficulty): Mr. Yang Sun!
Yang Sun: Mr. Shui Whatever-it-is!
Shui Ta: My cousin is devoted to you… because…
Yang Sun: Because I have my hands on her breast. Give me a cigar. (He takes one for himself, stuffs a few more in his pocket, then changes his mind and takes the whole box.) Tell her I’ll marry her, then bring me the three hundred. Or let her bring it. One or the other. (Exit.)

Yang Sun out right tells Mr. Shui Ta that Shen Te is dumb and that he is not really in love with her, but he is just going to use her to get what he wants. Shen Te hears all of these things and still decides to marry him. How can she be so naive when she already knows that the only reason Yang Sun is there is to get the three hundred from her and then he is going to take his mother with him to Peking. Not worrying about how Shen Te is to make a living after giving everything she has to him. She even goes all the way to actually getting ready to marry him.
How can she want to be with a man who has no love for her and not even look at the man who is willing to give up all he has for her and her good will, I guess a little bit of the irony here is that Shen Te has fallen in love with Yang Sun, Who doesn’t love her back, and Shu Fu has fallen in love with Shen Te and she doesn’t love him either. But yet in the end Shen Te is forced to choose Shu Fu in order to keep her business running and because he is the only one who offers her the money to pay for- anything she needs. Which leaves Yang Sun in the same predicament that he started of in, with no money to become a pilot and looking for a way to get the rest of his money, but not only that she thinks she is pregnant with Yang Sun's son. Which if she tells Shu Fu of this it will mess up her chances of getting the money and the help she most desperately needs to get back on her feet and to pay back everyone who she was in debt to.