First off, she's a cyborg and therefore partially organic. Second, he just wished to take the bombs out of 17 and 18. Third, she's one of the hottest chicks in DBZ and could easily beat his ass inside out. So clearly he has something appealing to her. He even got to put a baby in her.
*nerd mode: on* she's not just partially organic, she's mostly organic. just see her as a prototype of Cell, enhanced humanoid with bio-organic components. that's also the reason why cell needs to absorb 17 and 18 in order to evolve. the only mechanical parts in her and 17 are the bomb and the mind control device.