Why did you question her advise? Has she lead you wrong in the past?

maybe what we think looks "right" is just what we have seen the most and have gotten used to?

as far as a difficulty difference between putting side borders or end borders on first, I don' t see any

I have only been quilting about 3 years now; so I am certainly not an expert. However, I do the sides first, as I like the look of extending the top and bottom over the sides. I really do not know why it would make it easier to do the sides first. I just do it that way because I like the finished look of the quilt better.

I normally do the bottom first, then work my way up the sides. Why? Because if I'm going to make a mistake I'd rather have it at the bottom. quiltsRfun has the right idea, it is a matter of preference.