I agree with you all. Right now vaidika going through things and not to mention if sahil confess it's another problem. Gautam who is her age and a close friend is a safer route for her, which I'm sure she's thinking. I guess by agreeing to marry him, it will complete her family and she probably think he will be a good father figure to her daughter.
Second, her agreeing is probably trying to run away from sahil love. I mean his a young man, who she thinks is childish and irresponsible. Not to mention not her age. society already have problem with this, so to cause less drama and problems from society and his amma , she will move towards gautam who she thinks is the safest route.
She probably has feeling for sahil, but instead of figuring it out, she chose to ignore it. Anyway, I think the marriage won't happen leading to sahil stepping in to marry her at the right moment.