A time and a place
If you’ve ever watched a beauty segment on a morning show, browsed through the content of the swathes of beauty vloggers out there, or opened a magazine, then you’ll know that popping zits at home is a terrible idea. If it’s going to be done at all, then it needs to be by a professional in a clean and sterile environment.
In case you hadn’t realized, this means that you also shouldn’t do it on a plane. Someone didn’t get the memo, however, and now our OP has to put up with watching her seatmate squeeze her zit. That’s not something you want to see. This is not an acceptable use of your time on public transport (or any public place, for that matter).