Sorry to be slightly bias as I will tend to speak from a female's perspective
"I love her, thus I dont want to hurt her"
is always the reason to lie.
Doesn't this hurt her deeper when she finds out the lies? Well, unless you plan to break up with her with a beautiful ending, or else please be honest to her. Man knows the consequences of lying to woman; he knows he gotta pissed her off, but due to he manage to resound her with laughter, she will forgive the matter temporarily. Lies are like bombs in a romantic relationship, because the next time the couple has argument, there is a high chance that the woman will bring up the previous "lie" matter which totally annoys the man.
Man's mind : Over means past, why she wants to mention about that? Too free is it?
Woman's mind : He had lied to me once, there are chances that he will lie to me again.
Speaking from a woman's stand,
Lie creates uncertainty to a woman. The key point is she does not have the courage to trust the man anymore. The more he lies, the lesser she trusts him; even though she doesn't show it externally (which the man thinks he has got over it). If you choose to lie, you are choosing to break her trust towards you; thus, do not blame why she questions you again. Well, the man may later realised it was his fault and he wants to turn over a new leave, yet his woman still questioning him- man gets SUPER frustrated. Remember, you choose to break the trust, you need to pay much more hard work to rebuild the trust; unless you do not want her, that's a different story. If you love her why do you want to lie to her at the first place? Man always think that woman wants the best answer; in fact a real woman, who truly loves her man, wants the truth- she wishes to understand, to assist, and to be with him always.