If you're talking about romantic love, various reasons could be responsible for a person that you're truly interested in not to reciprocate your love. Before I would go ahead to list some of those reasons, this is one advise that I would want to give to you: "Don't beg, displease yourself, pretend to be who you're not, or cajole anyone to love you". Anyone that can't love you for who you are doesn't deserve your attention and love.

Ok, back to the question " why doesn't she love you?" Though your question is quite broad because it doesn't give any clue about how long you've known this person and the sort of closeness that exist between you two. Let me assume that both of you are friends or acquaintances. If this is the case, here are some possible reasons why she isn't reciprocating your love;

1. She's put you on the friend zone: when you act like a friend before a lady that you like, she would treat you like a friend; unless she's very much also interested in building a relationship with you. If she isn't, she would be very glad to keep you in the friend zone prison.

2. She isn't attracted to you: A lady that has nosexual attraction to you would never consider being in a relationship with you because you don't represent her idea of the type of partner she would want to be with. Attraction is a very key element in relationship building and falling in love. If she isn't attracted to you, it would be difficult for her to love you.

3. You've not let your intention known to her: most people would have left the friend zone long before they became permanent residents there if they had made their intentions known to their prospects. They kept acting nice and keep hoping that she would get the message. My friend, open your mouth and tell her your feelings for her. Invite her on a date and let her know your intention.

Friends don't go on dates. The more you keep quiet, the more you get placed in the friend zone and lose the chance of having her heart. Open your mouth and confidently tell her what you feel for her. It's better for you to know your standing with her, than for you to keep having hope in a hopeless situation.

4. You try too hard to get her attention : guys behave sissy-like whenever they try too hard to get a lady's attention. And no lady would want to be with such type of a guy. You gotta be yourself and let her like you for being yourself. Don't try to show-off or become what you're not because you want to get a lady. It makes you behave and appear stupid before her. Be yourself and don't put pressure on yourself to always prove yourself whenever she's around. If she doesn't like you for being you, acting like a sissy won't make her like you either. Stop giving your crush undue attention, it would get into the head of some of the and make the want to trample on you.

5. She has a boyfriend : being nice to a lady because you want her to leave her boyfriend is a very stupid thing to do. There are so many unattached ladies out there that would appreciate you attention and reciprocate your love gestures. Don't go on wasting your time on a lady that's still in a relationship with someone else. It makes you look selfish and stupid.

If a lady doesn't reciprocate your love gestures, there's nothing that you can do to make her change her mind. move on to someone that would be pleased to have someone like you and stop wasting your time on those that think that you don't worth them. You actually worth much more if you know your way.