As you note, you are using the encounter to evaluate whether you would like to marry her. That is, the encounter is not entirely platonic.
That may be so, but I have been saying good Shabbos to everyone since long before I was dating, and will continue to do so (community permitting) even after I am married, when there will obviously not be any such intentions. (Even now, I still say good Shabbos to my parents’ friends – such as the Rebbitzin of the Shul – and have yet to not receive a response.)