She's an okay end but it wasn't done justice. The mangaka tanked the series so the end was spoiled.>>153073509
I liked her but she is supposed to have a modest worldly charm to compare and contrast with the other girls and Keima. 'Objectively', she's meant to be weaker than others in terms of being attractive personality and look-wise (but grow in those respect, her look changes), however it's a matter of taste, like entertainment-value.
I don't feel she was particularly close to him. Keima is an asocial, reclusive person and closest to people he's obliged to be around, like Elsie and his mother. What Chihiro could do was break his rhythm and barriers, revealing different sides of his humanity. The Chihiro end is just really thematic, as Keima is willing to give a real relationship a chance, no bullshit.