Is it possible to terminate my apartment lease due to security neglect or any other reason without financial consequence?

The apartment is in a private home. I do not feel as if my landlord has held up her bargain to make sure it is safe. She has recently allowed people to enter my living space and do as they wish (including urinating on my floor). This was done in her absence. I confronted her right away, and expressed that I don't mind her inviting people over (it is her house) But I asked her not to do so until there was a lock for that part of my apt. Today, there is no lock and the same men are returning while I am away at work.They are returning to her separate apt in the home to do repairs, but how can I trust the same incident won't happen when they were originally under her supervision before?She claims she is buying a lock today, but has failed to provide one before hand. What steps should I take