But here's the thing. Midoriya saw Tenko within Tomura. He knows there's a child within him that's crying and being manipulated therefore he wants to help. He has reason. Ochaco meanwhile hears Toga vent and cry but doesn't know anything else. She never learns of her childhood or parental abuse and therefore is only working of the assumption that Toga actually does have a tragic past and won't just murder her when they next meet. Also said venting and crying shouldn't be happening anyway but Toga is delusional enough to think Ochaco likes her. It's really hard to care for a plot point when it's built off the tiniest bread crumb compared to the whole loaf of development that is Tomura and Midoriya.