It means to make something happen or appear through the power of thought. You make something happen or appear by thinking about it hard enough. It's a very new use of the word. It has only become popular in the last few years so it might not be listed as a definition in dictionaries yet.

It's B. Manifest is a trendy word right now. Manifest your success. Manifest your destiny. etc. etc. It just means to make it happen. Whatever "it" is. Manifest that scenario (that guy talking to you) into reality.

In this context, "manifest" likely means A. You wish. It’s unlikely. The phrase "I hope you manifested hard enough to make it happen" implies that the friend thinks the idea of the guy initiating a conversation is unlikely, suggesting a bit of sarcasm or skepticism. "Manifest" here refers to the idea of wishing or hoping for something, but the friend is implying that no amount of wishing or signaling will make it happen. It doesn’t seem to imply "displaying enough signals" (B), but rather a more skeptical take on whether your hope (or wish) for the guy to act will actually come to fruition.