At a risk of being pedantic she isn't 8 months pregnant, she's 33 weeks and still has 7 weeks to go.
She does look very well though, no bloating or puffiness. I imagine it's a combination of genetics, healthy diet and exercise.
With DD1 whilst I didn't look at all like that I didn't go into my maternity uniform until I was 26 weeks and only then because I couldn't do the button up on my skirt (military uniform.) I didn't buy any maternity clothes and just wore regular clothes a size bigger.
I'm only 5 foot 1 though and very short in the body so with babies 2 and 3 I looked like a Teletubby by 16 weeks...