Why do women love to lead me on?

Wtf? Why did you let the random guy walk up to her like that. As big as a guy as you are, the dude should be intimidated. If it was me, he would have walked up, and once he saw me he would have turned in the opposite direction. Why did you let him ask her for her number, that was your girl. That is disrespectful, to just walk up like that. I would have been like, "Hey bro, what's the problem? " "uhhhh, I. " "Back off man, she's with me. " Then I would wave my hand in a shoo shoo motion.

Now things become clear. Wish I'd seen this question instead of the other one you posted that was so cryptic.

First things first. Women flirt with no intention of having anything happen all the time. They do it for a variety of reasons. It's fun, they seek external validation, keeping their options open, etc. The list goes on and on. But that's not what's going on here. Read on for some brutal honestly...

On the flip side of things, you guys only knew each other for a short while, a month by your own admission. My gut instinct is that you came off as too needy and/or clingy and it creeped her out and killed any attraction she had towards you. Maybe that alone caused her to latch on to the other guy so you'd back off? Think about it.

Here's how I see things: You spent a month trying to convince her to "get together" and some random guy with the brass balls she's looking for (or is attracted to) just walked up and asked her out. In front of you no less! Of COURSE she's going to be attracted to him more than you. As for the looks comment I suspect that was her backwards rationalizing why she wasn't attracted to you any longer. If you've hung out with a woman more than 3 or 4 times and you're not into a physical relationship, you're in the friend-zone plain and simple. There's always a chance things may get physical, but you're be better off playing the lottery unless you develop the social skills to build attraction effectively.

Someone else had a question just like this and the answer is the same:

On the plains of hesitation lie the bleached bones of countless thousands, who on the dawn of victory paused to rest, and in resting died.
George W. Cecil

You didn't act and someone else did.

If she was engaged for the month you knew her, how did she lead you on?

Drop it and move on, if the two of them do get together and it fails don't wait around to pick up the pieces

You took too long and she lost interest in you. Its not leading you on, its you not creating attraction and losing what interest she has left.