How can I protect myself against a roommate who may be trying to kick me out?

I have a roommate, a long-time friend, who moved in two months ago. A couple of days ago, her son came from out-of-state to see her. She then told me he was not going back to college and would either sleep on the couch in our two-bedroom condo or at a friend's. I told her I was upset that she did not notify my sooner. Over the last few days, she has brought up several things about me that bothered her (this is the first time she has mentioned them). She wants to pay my landlord directly and I feel she is trying to move her and her son in and move me our. I am the only one on the lease. What should I do to protect myself?