Pennsylvania. That is her state of residence and where her income is taxed no matter where she earned it. Because her taxable income was so low for the year, she shouldn't have a filing requirement in any of the states she may have done work in (provided you did not miskey and hit 3600 instead of 36000. If the higher number, the situation is different). Her income may even be too low to file a PA return also, but it would be a good idea to file it there anyways.
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"