She's said she was tired from that new Project X Zone thing and told Chris to go on ahead without her. She'll catch up in the next RE.
Seriously, I wouldn't be surprised if Chris died this time around, he's been in RE5, Revelations, MvC3/UMvC3, RE6 and now Project X. All in the span of under 5 years. He's going to have a heart attack at this rate. : /