I didn't mean it like that😆
No mistress stuff
She is staying there as siya's physiotherapist. He could have just forced her to continue that by blackmailing or threatening her.
He also either wants to know her motive or maybe he has already got to know that she is working for someone else against him so only keeping her as physiotherapist won't help him to get properly ridhima . To make trap for ridhima & knowing everything from her then making her life hell for deceiving him it's necessary for vansh to stay under same roof with her. & only marriage can approve him to stay with her under same room legally. I think vansh wants to deal with ridhima everything legal way.