For Midoriya to react in such a way, the girl didn’t mean to make him so jumpy. That’s when Nensu assumed that she may have accidentally crossed the line when it came to the boy’s level of comfort. For her kind and gentle nature, she had to respect him, but clearly, even the slightest bit of contact would drive him over the edge. Would it best if she didn’t touch him, even if it was out of friendly intent? Perhaps so. With the ice cream to eventually arrive, Nensu thanked the clerk with a smile, before taking the spoon in hand. 
“I’m sorry if that was sudden. I figured I could help with your Quirk”, she said, having to offer if he has some trouble. They could practice together.