When I was single, I made it a rule never to say no after one date. It is a crushing insult to the other person, if they are interested. After two dates, there is still no real attachment, so it won’t break anybody’s heart, and it won’t be hurtful to their self-esteem if one says no.
Imagine if one gets a string of no’s after a single date. The person may think they are ugly and totally lose their self-esteem and confidence. This overrides any consideration of tznius and any other stuff. As somebody said before, menschlachkeit is the ikar and the only purpose of the Torah.