It is too early and hasty to take any decision against your marriage.
You should try to save the marriage till the maximum extent and after that if the situation is compelling or beyond tolerance you may decide otherwise.
Such type of immature behavior or common among the newly wedded wives because they are not exposed to outside world and in fact their impression is that anything which is against their choice or wishes is nothing but an ill-treatment or cruelty against them.
Their parents are the culprits in most of the cases who will not even be bothered about the future of their children because their selfish motive mentality is the one which is misguiding and spoiling the future of their children.
For the present you may remain silent for few months and allow her to change her mentality in this regard but you should remain firm on your decision and not to budge to any pressure from her side.
They may probably send her to your home once the child completes five or seven months, if she is not returning until then, you can issue a legal notice asking her to return to the matrimonial fold.
If she is not willing to return and instead if she resorts to file dowry harassment case, then you may challenge her false case by first obtaining anticipatory bail and then confronting her in the trial proceedings properly.
Observing patience would be the option before for the present, which itself would bring lot of changes