I just assume that it was a typo, until I read another sentence: Please try to come in before 5, sense I need to leave by 5:15.
And this girl is a master's student at an Ivy league school. She is a white American, born and raised in New York State, so English is her first language.
What are grammar and/or spelling mistakes you've seen that have appalled you? I'm mainly interested in hearing about ones that are made by people whose so-called native languages are English.