I'm sorry to hear about this. If you're okay with answering this - why is she shouting at you? That seems extremely unprofessional and she shouldn't be doing that - there are better ways to communicate things with a student then that. In regards to her following you into the toilets - this may just be a coincidence and nothing more than that. If her behaviour persists, try your best to stay civil, so that this doesn't reflect badly on you and speak to your student rep / personal tutor or a member of the student union in regards to this situation. I had a situation in which I wanted to move tutorial groups in first year, but I later found out that this wasn't possible at all and it might make things awkward. Don't let her attitude affect your studying, it would be worth going to those tutorials and seeing what happens - give it a try and hopefully it'll be fine, but if you really don't feel good about it then it would be worth doing as I mentioned previously. I hope things get better for you.