Because she is less than agreeable when being handled. Snakes are temperamental creatures, they have no capacity for emotion; it isn't that she doesn't like you. You just happened to get a snake that is not comfortable with being handled.
Older snakes that are uncomfortable with handling tend to stay that way. I have a handful in my collection that will hiss, strike, you name it, whenever I try to handle them. Others I have couldn't care less about what I do.
Also,
When you get a new snake, it is best to leave them alone as much as possible for the first couple/few weeks that they are in your care. It gives them a chance to transition into their new surroundings. She could also just be cranky from the move.
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