Tragedy in Balika Vadhu - Pratap dies, and Sugna becomes a widow

Balika Vadhu specializes in showing the tragedies of life, concentrating on social ills that are prevalent in society and are accepted (and which we need to put a stop to). So, you have a household in rural Rajasthan, where there are all sorts of unacceptable social problems such as child marriage, shunning of widows, high interest rates, the subjugation of the parents of brides, and so on. In this case, the major perpetrator is the matriarch of the house, the grandmother who has her own old beliefs and rules the house with an iron hand.
So, when she essentially bought the young girl, Gehna, as the bride for her elder son, she also sought to implement her iron rule on Gehna, and Gehna would rebel frequently, being crushed every time. However, Gahna suffered majorly when she found out that she was pregnant; in spite of being told by doctors that it was unsafe for her to give birth to a baby, there was very little chance that she would be able to do as she wished. In the end, her parents were called, told that they would have to suffer for the rebellion of their daughter, and finally Gehna surrendered.
The serial is very clear that it wishes to show ill-practices happening, and is willing to show as much pain as possible in order to showcase what it wants to show. In order to drive home the point that child marriage and marriage at a young age, combined with other social ills, are major problems that society should depict, it takes the 'gauna' (departure of the young bride finally to her in-laws house when she reached maturity) of Sugna to drive this message home. So, after showcasing the pomp and show of the 'gauna' ceremony (although it shows the pain of the parents of the daughter-in-law of the house in having to even sell off their land so that they can give appropriate presents at the ceremony), the show reverts back to its theme. The young son-in-law is killed by dacoits while coming to the house, and for sure, Sugna will be shown as a young widow, to be treated as badly as any other widow. Maybe this is being shown to drive home the concept that it is only when somebody of the family becomes a widow do you realize the pain that these abhorrent social practices cause.

Videos of the killing of Pratap and reaction of Sugna