Spoiler alert: Obviously many of you got this movie very wrong....
There was no "love" story. The connection between the white woman//black male was of survival. She literally says to him "we have to do it" ...meaning pro create because of "near extinction", essentially.
She didn't "kill" herself either....
She built up an immunity and was able to Adapt to the toxic environment..hence the child at the end of the movie...hence the multiple refrences about her stomach//scaring...
Don't get me wrong the movie was certainly slow, boring, and honestly should have been set up as a tv series to fill in all the missing gaps that left us questioning certain things. However, a lot of people missed the scientific basis of the movie by interpreting the plot with "civilized" overtones. Not the case.
The movie was pretty disappointing overall. If you're bored and have binged on everything else, go for it.