I'm not a great person to give you advice here since you'e got a month on me. But it could be a temp-check thing. If it were me and she is with OM, I would just ignore it. Or say something very benign like "Thank you for letting me know." She knows this is something you guys did. It means she's thinking about you enough to remember that you wanted to watch the next season. If she is genuinely second guessing, she will keep trying to contact you. It'll become more obvious. Maintain the mystery.
The poke the bear option (which I wouldn't recommend) is to say "Yeah I already watched them." :-p
But hang tough. I Feel you, H and I watched the walking dead. WE stopped this last season (now I know why) but if he texted me about it, it would throw me through a loop too.
M:26 H:32 T:8yrs ILYBNILWY/ "I'm not happy": 2/6/16 D-Day-discovered PA/EA: 2/10/16 Separated: 2/14/16 He's living with OW I moved to different state: 06/16 Currently: Trying to move forward