Thanks everyone for your advice. We did not sign a legal contract, which is why I was afraid I didn't have any lease-holders rights. She forfitted her keys to me when I payed her the first months rent and the security deposit, but I was (stupidly) unaware that she had a spare set of keys.
Believe me JerseyGirl, I am extremely concerned about her barging in when I'm not here! In fact, it is my belief she thought I wasn't here. I live on the second floor, and my bedroom windows face the street. She could have seen from the street that none of the lights were on.
I am a peaceful, loving, and empathetic person. And when she barged in, I was so irrate and just flat out SHOCKED that I decided not to interrupt the long-distance phone call I was already deep into, and just ignore the situation. Before she left she stated "we need to talk" and I told her to either call me or email me. When she does, I will be making it ABSOLUTELY clear she is to contact me before. If she has a problem with this, I have no problems moving out. I didn't legally sign anything saying how long I would be living here, and yes it would be a horrible inconvenience to move. But I will not allow someone to burst into my sanctuary like so. She didn't even have the courtesy to ring the bell!!
"What a mystery this world. One day you love them and the next day you want to kill them a thousand times over." The Masked Bandit in THE FALL