I used to think, if I say "I like you" and she reacts badly, she doesn't want me and I didn't waste more time talking to her. That I did everything I could and I wouldn't have to blame myself for losing an opportunity. Then I got more and more often the reply "I cannot say, I need to get to know people". I felt tested, but not in a good way. More in a "I don't find you attractive. But I am bored, and I am going to mess with you a little, giving you false hope". Then I read that women actually take some time to like someone or not, but you have to convey personality. Then I talked and talked and it went nowhere. She "realized" that I wasn't interesting.

Also kino: when touching her and she blocks me, how can I tell that it's not just a temporary no?

In a nutshell, what is the shortest way to really gauge a woman's interest (even if she is with another man)?