You can start doing reality checks now if you want. Some say to do them a dozen times a day at random. Some say only do them when you see something out of the ordinary. I'm guessing a hot pink car or an insane looking Mohawk on someone lol. I personally only do reality checks when I think about lucid dreaming. If I'm at work or school and do not think about dreaming or LD for hours at a time, I will not reality check. But when I do I will RC. This unknown girl is your dream sign. Every time your think about her or dreaming do a reality check. She will not tell you who she is, but you can ask her when your lucid, and that will be an experience haha.
Have fun