1) No she doesnt need it. She can sign paper as long as she understands it. However, her inability to speak english can pose another problem. During her interview, her english will be tested, and since she doesnt speak, it will be you burden to prove that you can speak spanish fluently. (this usually a problem with asian fiancees, in your case may be if you have strong latino roots, they will be easier on that).
2. No all pages of passport only for US citizens passport. But just in case, copy all of them.
3. Yoes you need I-134. The form is tricky in itself. Read carefully guidelines and follow them. Basically youneed to prove that you are making some mone (like 15000$annualy for two of you).
General comment: most of your questions are simple, and I encouridg you to go to www.uscis.gov
to read instructions to K1 application kit. Asking questions on YA may or may not give you a correct answer. I saw numerous erroneous answers.