We only know for sure it felt a special kind of attraction, it tried to seduce her to such a degree he ignored Parker. The way the alien moved slowly towards her after killing Parker felt like some kind of love walk.
The mysterious behavior of the beast and the sense of mystery of the SOS/warning call and spaceship and the eggs and fossilized creature all combined gives this film an otherworldly feel that has never been matched by any other space film.
We're still talking about the mystery behind it all 50 years later. Absolute perfection. Nothing ever needs to be explained, let our own imaginations terrify us.