Don’t surprise her with a proposal. How you propose can be a surprise, but not that you will be proposing. Make sure she will be comfortable saying yes (that it is not too early).
You should have had conversations about a life together. You should have had conversations about a possible date for an official announcement of your engagement.
Many people keep the shadchan involved throughout the dating so they can find out if she is ready for the life-changing question.
Related: