In the very beginning of the show, we got a glimpse of Ishwari's possesiveness about Dev when there was a rishta for Dev. She refused it. Also whenever GKB wanted to get alliance for Dev, Ishwari was shown as very uncomfortable with the idea of Dev getting married to a girl. Ishwari liked Sonakshi as her nutritionist but not as a prospective daughter in law because she did not want to share Dev with anyone.
Regarding Soha, right now she wants Soha for herself as Soha is extension of Dev. Not sure what will be her reaction if her interest and Soha's interest clashes in future.😊