In writing, you can tell if it's "her" or "you" based on whether the pronoun is capitalised. If the pronoun isn't capitalised, it's going to be her; if it is capitalised it'll be "you." When you're listening to the language being spoken, however, there won't be any difference in pronunciation. In that case you can tell which it is simply based on context.
That doesn't work. There's a difference between "jemanden einstellen" and "etwas einstellen" Jmd. einstellen = to hire someone
Etwas einstellen = to stop something Wir werden die Produktion einstellen = we will stop the production Er stellt das Projekt ein = He cancels the project
"Etwas einstellen" can also mean "to adjust". Das Licht/die Lautstärke einstellen = to adjust the light/volume