I like a female colleague, but she won’t reply to my messages. I only said hello when I met, and I didn't have a chance to chat with her. I'm giving up. What do you think?

This depends on the situation.

First of all, if you send her a message but don’t reply, this is enough to show that she doesn’t feel in love with you.

Secondly, greeting you when we meet is also based on the fact that you are colleagues, not the kind of male-female relationship you think, and I have good intentions for you.

Third, make sure the other person is single, otherwise things will be very embarrassing.

Fourth, I wish you good luck.