It maybe just that an ear infection that came along with the RI, If you can add an anti inflammatory to her treatment it may help to reduce possible swelling. sometimes the head tilt stays permanently. use your judgement on it though because if the balance is so off the rat will start rolling over and it wont be able to eat or drink. But other issues may cause head tilts as well such as strokes or tumours. If you want to try and help her, give it the old college try. But I wouldn't hold it against you if you went the other way either.