She may have been harboring those feelings for quite a while. She may have told you those things hoping if she said it enough she could convince herself it was true. I know I did it with my gf about moving in. Eventually, you realize you cannot convince yourself what isn't true. She said she was going to sign a 6 mos lease and I was glad. It relieved a ton of pressure that I have held inside...we had a really fun day because I wasn't hiding anything...or having other thoughts.
I think you should take this as a sign to get out.