She is probably telling you the truth when she admits to your making her happy and this relationship being the most normal one she has experienced. However, prior to this, I assume she was in an alcoholic fog. She is expressing her appreciation for what she had, but it does sound as if she is ready to move on.
Discussing options ... hmmm. This sounds like a red flag to me. Whose options? Her options? What about YOUR options? It sounds as if she has made up her mind to control what direction, if any, this relationship shalll go.
A relationship of just four months is not an investment in a lifetime together. I would suggest you look at the red flags waving in your face. Minnie is entirely correct ... someone who is entirely different with their partner versus family and friends is not a good sign.
So you have someone who wants to keep her options open (I read this to mean, she'll take up with you if she wishes to use you or nothing better is on her radar scope) and she is entirely different around you. Just a brief bit of personal experience: my AH was considered the world's "nicest guy" and "one of the good ones." Yes, he had a good many people thinking he was quite a catch ... until I "caught" him. I was physically, emotionally, and verbally abused.
One of the good ones, my arse!