"¿Harías eso por mí?"
Translation:Would you do that for me?
I made the same mistake. I'm no expert, but I have a theory that it's because the word "por" is being used instead of "para." "Por mí" means roughly, "in place of me" or "instead of me," while "para mí" would mean "for my benefit." The speaker is asking the subject not exactly to do a favor for her, but to do something on her behalf. As in, at a restaurant, "would you order my meal for me while I'm in the restroom?"
"Make" in this context is a little less plausible; when someone makes something for me (like a scarf or a watch), they're not doing something on my behalf, but for my benefit, so it would be "¿Harías eso para mí?"
Since we have "por," it seems more likely that it's "do." (Although if I push it, I can make a case for "make" too.)
Native or advanced speakers, if you're out there, let me know if I'm on the right track.