Balika Vadhu did not show bal-vivah wrong. Bhairo- Sumitra had a blissful relationship, even in Anandi's generation - there are normal relationships like Lal Singh's, Phooli and Sugna got widowed - that can happen even in adult marriage too, Rani was abandoned - that also happens in adult marriages too. Anandi remained with less education and was made to do household works - it was more due to DS's rigid frame of mind (and her parent's hurry to do gauna) and less due to bal-vivah. Generally, in bal-vivah girls remain with their parents and go to sasural after gauna, which takes place a lot later.
Even after marriage in adult stage - they show Anandi returning to Singhs is just a little short of glorification of bal-vivah. Even a glamorous, bubbly Nimboli does not make impression that she is suffering. And before anybody assume that I want to see torture - I make it clear - I do not want to see torture - but make the tortured girl look and behave like a tortured girl. Otherwise it will be same feeling which emerged when Rasika was weeping in front of Shiv telling about her torture...
Rasika was an adult while Nandini is too young. We have seen how roughly Harki and her husband handled a small crying infant. Anandi was brought into BH with her parents consent and blesssings and Nandini was not. Rasika was clever in that she convinced Shiv about her torture and sob story. Only the viewers could see her deceit.
As you said, Bal Vivah can work in some cases but the consequences like early motherhood can be disastrous.