Why is my cat viciously assaulting me!?

My kittles has been around 2 years now and i got her when she was a baby. i raised her and ive always been the favorite and she sleeps with me and the whole nine yards. i am not around as much as i used to be because i moved to the city. i went back home a few days ago and things were fine like normal but i was with mom and i was about to sit down and suddently her hair stands on end all over tails bushy she starts spitting and hissing and howling and moaning and attacking my ankles. it was quite a show. i left and came back and even at the sound of my voice she was flipping out even to the point where she tried to chase me into my room and if she seen or heard me she was start to put on the same display. she has been spaded for a while and i think she might be in heat. but idk if its even possible to go in heat when you dont have your reproductive organs. what could be her problem!!?!?