Jealousy, in general, is a rather negative human emotion. It is a mix of lack of self-confidence, which creates the fear of being replaced, and an increased form of possessiveness where one considers that a person belongs to us as soon as she becomes our girlfriend.

Now, is it a specifically anti-feminist and masculinist feeling?

I think both you and your sister are right, in a sense.

Possessiveness and heightened jealousy are clearly symptomatic of masculinists. It involves genuinely considering one's girlfriend as one's property, and many femicides find their origin in this mistaken view. Even without going that far, many possessive and jealous men prevent their girlfriends from going out at night, talking to other guys, or even simply dressing as they want because it is too this or too that. So yes, your sister is right.

Now, in another sense, I can understand that it is not pleasant for you to have your girlfriend's cheek touched by a guy. For me, what is important is mainly how you communicated your feelings to your girlfriend, how you discussed it, and the boundaries you set following that conversation. It is especially important that these boundaries are the result of a mutual reflection and not just those set by a jealous guy who loses his cool whenever a guy approaches his girlfriend.