if the "so-called" muslim isn't practising, yet STILL believes in the shahada, then he is sitll a Muslim, marriage to him would in no way put it at par with zina.
Secondly, if he hides from a girl his true feelings (or lack of) for the religion of Islam then its not the girl's fault is it? she's not to blame of zina or whatever bcoz of her ignorance to the truth.
That's ok... you didn't get the question....
Rest, I agree with your second part...