You say that she is talking to you often, calling you little nicknames and putting her hand on your shoulder. Preumably you have watched her enough to know if she treats other guys similarly (particularly the physical contact). If she is the type that touches other people casually/frequently then maybe you are reading too much into it. However if she is not making physical contact with other guys at the dojo then I think she is really trying to tell you something!!!
There is an old saying something along the lines of:
Three things come not back -- the spoken word, the spent arrow, the missed opportunity.
Don't miss an opportunity that you may regret for many years to come. Good luck!