C'mon dude. A relationship is a full-time deal, should've called her when you heard, or at least had a text convo with her to try and help her out.
Although I don't know how busy you were at the time, from what you were saying (Playing video games) it seemed like you had some time on your hands.
And anyways, you should be the slightest bit understanding that she was on meds (From what it seems like) so that would defiantly mess with her mood.
I'd be mad at you too if I were her.
What you should do is apologize, and try and ask her what's wrong. If you can, try and make her feel like she can get to you anytime if she needs it.
Me, I get "depressed" (Not sure if its clinical depression just yet, should get checked out) and I know that my bf tries to help me out of it, she may just need the same thing right now.