She's asking why you love her and not another girl. Why you picked her and not another girl. She loves you, she just wants to know why her. Girls tend to have this thing of pointing out EVERY flaw we have. And that leads us to wonder why a guy would choose her out of all the other girls he could have. She's grateful and happy it's her, but also wants to know why it's her when she has so many things wrong with her. Girls are weird like that, we're never quite good enough is how the majority of girls feel which is where this question tends to come from.
It could also be that she just wants to hear you tell her the things that you think are amazing about her. She does this because it makes her feel good about herself and that you guys are actually in a strong and secure spot in the relationship where you can be sweet like this and not worry about anything.
That easy it's because we want to know why? Not just because we are pretty we lol knowin that the guy likes us for a unknown reason lik he loves my laugh or we hav everything in common.. If a guy truly likes a girl than he should hav no problem answering the question
I asked my ex boyfriend that question once and he asked me back. Well, basically, girls ask that question to know what about her attracts you? She wants to make sure, that you are not the type that would be like, 'Baby, ur sexy...' She wants honesty and concrete answers. Like, what made my ex boyfriend wanna be with me, was my style of talking, and how I was not afraid of adventure. As for my friend, her boyfriend liked her kisses. It is diff for every situation. What do you like in ur girl? Her eyes, her lips, her character, her laugh... answer her question... :)
We want to know what differences you like so much from another girl that you picked us instead. It makes us feel more secure and confidant that we are winner in your eyes. Giving us valid reasons confirms that you love us for who we are and are not just using us for other things.