Well she pulled the bitch card, so now you just have to pull the MAN card. Go to the office and tell them what's going on.
Tell the office manager that you tried to be cordial and politely asked her to let you park in your space, but she totally blew you off. Then tell them that you think it's silly that it even had to come to this situation. You'd like them to resolve it as soon as possible. Also, tell them a horror story about how you came home late one night and had to park a whole four buildings down.
If she keeps doing it over the next week or so then the office hasn't done their jobs. Let them know how that it's fvcking bullsh!t, and if they obviously don't care about assigned parking then you will park in another guy's spot.
As far as your neighbor? Fvck that girl. You tried being nice, but she wanted to be a bit*h about things. I would act in my best interest only and not give two sh!ts about her. Even if she had four kids, three jobs, and still had to do sexual favors on the side just to pay rent. She can park her shi* on the south side of the river and thumb a ride home from a desperate meth addicted trucker who hasn't gotten laid in eight months. Basically, show her your care-face.
But I'm just cutthroat like that. You could just take it and have somebody walk all over you