Most Helpful Guy
Some girls, as in a small minority, sure. Nothing to write home about. The opposite is true based on my observations. Acknowledge her. We all like being acknowledge to some degree.
Ignoring only breaks the bridge of communication between the two of you, and crazy thoughts can manifest in her mind in the meantime without your words shunning them. Just read some of these questions about girls trying to draw conclusions out of the simplest, dumbest gestures.
"He added a girl that I hated in 9th grade on FB. Is he cheating?"
"He texted "ok" when I asked if he was having fun. Is he lying?"
"He liked an IG photo after he said goodnight. What is he hiding?"
You definitely do NOT want to ignore a girl you care about. Imagine letting these thoughts run wild without your dissenting voice clearing things up.