If she were in my class, it wouldn't be accepted! However, online, it is a word. It's "short" for probably. There's a lot of "short fors" online now. Some of them, I was too embarrassed to ask about, but now I know them. Much the worse for the English language, they are becoming accepted in mainstream conversation, and even more formal communications. That's why the letter and even phone call are dying out, and more people use email, text messaging, and even voice mail, and do not actually speak to other people!
(There you go...soap box about the death of the English language...as typed on a bulletin board! )