I'm going to ask a woman when the baby is due when she isn't actually pregnant
That is horrible! Why would you say that to her?
There was this woman who told me she was 6 months pregnant, that's why
You should never ask a woman that unless they tell you that they are pregnant. Commenting on someone's weight like that is hurtful.
What if she was fat? She looked healthy to me.
It doesn't matter what someone looks like, you shouldn't comment on their weight. They could be going through problems or it is a sensitive issue. From now on just comment on something else about them.