She clearly doesn't like the music that you play on your guitar!!!! Take note! (only joking
Do you have a cat flap? If not, she might be weeing by the door because she wants to let you know that she wants to go outside, or (like my cat) is making a statement that she is not happy she is being made to stay inside.
Did there used to be a litter tray near to where she is doing her buisness? Has a cat ever done its buisness there before? If a cat can smell feline poo/wee in a certain spot, she will think its normal and perfectly ok to do her buisness there.
Best way to deter her is to rub vinigar into the carpet to get rid of all of the scents. Try it, and see if it helps!