If accents were important to a career, how far would Henry Kissinger have gone? Just the first to come to mind. If you know your stuff, you know your stuff. Most lose some, a few, all their accent after a few years in a new environment. Personally, I wouldn't worry about it.

Your comparison of English spoken by Russian students to that spoken by Japanese, Korean and Chinese is leading to where?

Based upon what you have written here; I'd say Sarah is a very confused girl.