From Prerna's POV:
There is a problem regarding her family coming to the streets.. And possibility of losing everything valued by her family - self-respect, pride and dignity.. In worst case she may even lose one of her parents in bringing the problem to their notice..
And if she hadn't had any options then she would've at least thought about what to do.. Mohini gave a solution to her problem in a silver platter.. i.e. Marriage with Navvu.. And the way she has taken this extreme step, it appeared to Prerna that Mohini can go to any other extreme too, to trouble the Sharmas for not giving what she wanted.. To avoid all that Prerna has the simple solution in her hand without bringing any more hassle.. For Prerna it didn't bother much getting married to an elderly man.. All she has to do let go of personal wishes and dreams.. That's the simple sacrifice from her end as a token of her love for family. Of course many marriages happen just for the sake of it.. Kinda settling down as a duty and to continue the generation.. That's all.. And here it came as a marriage proposal from Mohini for her own brother.. A man who thinks that the girl is beautiful and want to marry her. That's all to it.. And if Prerna agrees to it, that's all.. Everything made simple.. Her family will be safe from any more problems.. If they get to know the problem, then even this simple solution will be lost from her hands.. From her POV, keeping her family's respect protected and having them safe and secure is more important than anything else..
And if her parents get to know the problem, they definitely will not be able to accept Prerna's solution.. From their POV, keeping their daughter's happiness and wishes will be important for them.. That's what her parents are and will be when they get to know.. But that's their duty and love when it's their turn to express..
Rught now it's time and focus on Prerna's duty and love 😉
And yeah, as you mentioned she's just accepted her own decision and willing to face it head on with whatever courage she has in her.. She's still living her life in her small moments.. This is how she would be living it, even if she is married to any X or Y or Z.. When it's a marriage of convenience, there's nothing to bother whether it is Navvu an elderly man Mr. X a handsome young man.. But when it's gonna be out of love i.e. Prerna's kinda love then everything will be different and all will be dreamy again for her.. And nothing like that happened to her yet.. Till then it's just another regular event.. She's just taking it as it comes.. 😃