I don't think anyone "deserves" success simply because they work to achieve something.
And just because Momo took extreme measures to meet a visual standard doesn't mean she "deserves" it anymore than others who worked hard in other areas.
That said.
While I don't endorse such an extreme method for losing weight so quickly, the larger context can warrant praise.
Momo working to achieve a visual goal and attaining it is something worthy of recognition.
Visual aesthetics are foundational to kpop.
Working on improving visuals commonly contributes to probability of group success.
Momo worked to improve herself to help both her own success as well as that of her group.
That's worthy of praise even if the exact methods were less than desirable.
It doesn't mean she "deserves" anything though.