Just do it
A lot of the pictures from earlier showed people sticking their feet and hair in places they don’t belong. Here, we see a woman resting her hands behind her armrest and in full view of the person behind her. It took every fiber in the OP’s being not to hold this woman’s hand and make her uncomfortable.
We say you should’ve just gone for it. There’s no way your flight could be any worse, right? After all, she’s raising her arms, allowing armpit odors to waft into the recirculated air and poison everyone on board. If you touched her hand, she probably wouldn’t put her arms back down but not before chewing you out for vIoLaTiNg hEr sPaCe.