I think among other reasons, the no.1 reason why Adi-Sumo marriage shouldn't happen is because Sumo looks like she is heading to her slaughter.
She feels like every one she loves wants to get rid of her...Shravan, her mama-mami, masi,etc...and even Nanu is being passive-aggressive about her marriage.
I feel sad for her. I am not happy with some of the things Sumo has done in the recent past. But I hope she doesn't have to suffer being married to a man (Adi) when clearly she loves another (Shravan). Adi-Sumo are just not compatible, IMO.