This may sound pompous but I hope not. Remember that you are in control of your reaction to her actions.
She seems to lack control in her life, as suggested by others on here.
People have sometimes teased me relentlessly, and I am sure others have suffered the same at times. Wait until the right opportunity occurs, this make take some time. Then anonymously seek revenge. The half-eaten apple is a mild retribution, it is not for me to suggest anything stronger.
One extremely very troublesome person that I had to deal with, was quite happy to allow a truck load of pigs (the animals) to suffer in extreme heat at a Motorway services. She refused to assist me, when I knew she had the experience to help with the problem. She would not, because she said she had urgent work to do. (She was processing invoices, I was trying to assist a Vet inspecting said pigs). I did not muck about, went straight over the top of her head, as it were, to sort things with our Chief Vet, who then personnally got involved. I think she was gobsmacked to put it politely, that I was prepared to do that. I also think that he may have hidden, when he saw her approaching him.
I avoided complaining about her, she had been trouble for many years. I gained confidence, in knowing that she could **** off, I did not need her help. The point I am making here, in addition to the "revenge" suggested earlier, is that you rise above her petty reorganising etc. I know you have said there are circumstances you do not want to mention, so it is easy for me to say this, and harder for you to stay calm.