I agree, probably do nothing save give general words of encouragement. It is early in the academic year and things may improve.
Bear in mind also that at Oxford it is the opinion of the examiners which matters. The tutor's opinion of essays written in the first term of the first year will have no bearing on what classification the examiners award at the end of the third or fourth year. There is little to no formal marking of course work at Oxford, in most undergraduate subjects.
Also, there will be other subjects to come, with different tutors. It used to be the case that, to get a first, you needed what was called a leading alpha in seven out of ten papers. The modern equivalent is numerical, but even the best student can slightly fluff a paper or two and still do well overall.
Not every tutor has an easy personality or is a great communicator. The more old fashioned tutors tend to believe in throwing people in at the deep end, and see the learning process as a form of dialectic. My own main tutor, whom I liked and admired enormously, described the tutorial as "intellectual single combat between teacher and pupil". Sometimes the looked-for good working relationship with a tutor doesn't quite gel. But everyone will be taught by several tutors over the course of a degree.
The tutor's bark may be worse than his or her bite. Most tutors will be receptive to questions, and to a student saying "I don't understand."
Your daughter deserves to be at Oxford, of course.
Ideas when fed up: browse the books in the Norrington Room at Blackwell's. Walk around the prettiest part of your college (if it's a pretty college), or one of the most magnificent colleges (John's or Magdalen, for example; ignore any closed or no entry signs, you're a member of the university and the signs are directed at the tourists). Walk in Port Meadow or the Parks. Go to the Ashmolean. Stand in Radcliffe Square, and then go and sit in the Radcam or the Old Bodleian. "I belong here. This is my place."