Nensu honestly didn't know how she would be able to relax the tension in the air, as well as that grim tone left behind in the aftermath. She fidgeted with her fingers a little, as she watched the scene before her, still trying to find the right words to help ease the situation, and the woman's worries. This was Izuku's beloved mother, obviously. 
So, what could she say?
Just by watching the scene, it made her think about her own mom; the one who actually held faith in her own children, and who would do anything to support them. It only made her wonder whether if she was doing okay in the hospital, and it also made her realize that she hadn't visited her; one of the few figures in her life to actually support her dreams, and reassure her that she was okay. Now, with having to cross paths with Midoriya, it was as if he had the ability to conquer anything thrown at him. No one in her life, did Nensu ever think, would be able to survive Loma's wrath; let alone [i]stand up[/i] to her, and not be afraid. 
Izuku seemed confident enough to help her, and he proved it, after he showed her the first sign of romantic intimacy. 
It jumps back to the question that the kind woman was able to ask her. 
"Oh! Nensu Todoroki, ma'am! I’m a classmate of your son's, and...we're dating."
She nervously added the last bit.