Honestly I have no idea how she has a silver nugget. She makes very little effort to actually communicate with her students unless they are fluent in Spanish. She gives no warning of when myspanishlab is due and if you try to have a conversation with her after class, she refuses to speak in english, even for students who are not good at Spanish. She is frustrating and does not efficiently explain her homework. I would not recommend her as a teacher unless you have very strong Spanish speaking skills.
Mercedes is an okay teacher. She can be kind of passive aggressive, and unclear about what she wants. I wouldn't recommend her if you're really interested in learning Spanish, and she's not an easy A by any measure. She's just okay, nothing special
I found Mercedes to be a great professor! I had her first semester of my freshman year, and I was really nervous to see how language classes would be conducted in college. I took 4 years of Spanish in high school, but have always struggled with it, so needless to say I was terrified on the first day when she only spoke in Spanish! However, I am confident to say that my spanish skills immensely improved after taking her class. She conducts every class entirely in Spanish, which really is the best way to learn a language. It only became annoying when I had to ask a question and didn't know how to say it in spanish and would feel awkward asking it in English. Class time is usually devoted to working in small groups, which was helpful because it was a great way to become more comfortable speaking Spanish. She's a tough grader, but if you put in some effort and actually do the homework exercises getting an A or A- isn't too difficult!
Mercedes is highly motivated and tries to get everyone to learn. If you're primarily interested in another subject but need to fulfill the language requirement, RUN! However she is a very harsh grader compared to every other class I've had at Columbia. According to my transcript, only 13% of my section received an A- or better last semester (my next lowest class is 29%, with most in the 30-40% range). This semester I have her again for Elementary II, and I expect the same thing. We've had a few compositions, which she usually grades and has us revise to resubmit (the final grade is an average of the two drafts). I never find her comments helpful, and my grade on the revision rarely improves very much. Lots of grammatica and online My Spanish Lab homework every class. I don't think any of this is particularly atypical. She loves making these powerpoints out of the grammatica book to illustrate stuff, but they're rarely very helpful to me. She has us spend a lot of class working together in small groups of 2-4, which can be helpful but there's little feedback on what we're doing wrong.
Mercedes is pretty good. She has reasonably high expectations for comprehension, and pretty much exclusively uses Spanish in class. However she isn't cruel if you're clearly struggling, and will drop a few key English words or write things on the board, etc. She does lots of in class activities in small groups of 2-4. The grading on the compositions was a bit harsh. I know many of my classmates got spanish speakers to write (or sometimes just proof read) the compositions. I think that hurt the grades the rest of us received, although it's hard to say. The exams were standard for the department, and not too difficult. While she's not amazing, if you're willing to work a bit more than some other classes I think you'll get a bit more out of her section.