Don't be discouraged. Many of us had similar experiences during the fundamentals course. I had an instructor who spent half the class cracking jokes and most of the other half talking about her personal problems. Her exams hardly had anything to do with the material covered in her lectures, and she certainly taught me a thing or two about how to learn independently.
My suggestion would be that you keep asking your instructor questions about the topics in the program outline whenever she begins to go off on her tangents, and also try to learn as much as possible on your own. The important thing is to stay focused and to learn everything you need to know to pass the class and move on. Get the course outline and study all the chapter materials indicated. Make a list of all the stuff you don't understand and ask the instructor a lot of questions about them in class.
When you study, don't just try to memorize definitions. Make sure you understand the concepts. Always think about the bigger picture (i.e. what are the nursing implications; what type of interventions are indicated or contraindicated, and why; how the nursing action impacts the agency, the patient, etc.) Nursing exams are mostly critical thinking and nothing at all like exams for other courses. Therefore, you can't study for them the way you normally study for other types of exams. Get a book with NCLEX type questions to practice with, and be certain to READ all the rationales for the answers given. After you've been practicing these questions for a while you'll get better at reading and understanding them and also at choosing the MOST correct answer from a tough multiple choice list. Ergo, you'll feel more confident about sitting the exams, and you'll get better grades.
Get a clinical skills book and use it as a guide when you're practicing in the lab (i.e. Clinical Nursing Skills and Techniques by Perry and Potter). This is an excellent book because it gives step-by-step instructions with photo demos for pretty much every clinical skill. You can also check whether they have the nursing videos
that cover these skills in the lab or in the reference section of the school library.
Finally, find a steady partner or a small group to study and practice with until you feel comfortable and confident with your skills. Get the study guide that accompanies your textbook and use it to help you focus.