Everyone has missed the one question that can provide a lot of insight – @megs, where do you live? If your profile is correct and you live in Canada, that’s a bit different from if you live in Afghanistan :)
Regardless, they are either staring because you are beautiful (very true) and are sad they cannot get with you, or because they think girls dating girls is a sin or abhorrent. To them, I say eff off. If you are happy, that’s all that matters! Life’s too short to care about what strangers think of you and your girlfriend. Just know that some of it, I would say most of it if you live in Canada (but maybe less if you live in Alberta, the “America” of Canada) is outright jealously. I say this based on my personal experience with Canada as well as people of all types who live here. While some people, especially the elderly, find homosexuality offensive, the vast majority don’t see any problem with it and thus disgust would not be the primary cause for their looks. So when you see someone doing this, just smile to yourself, for you have won over them, you take their hate and deflect it while also observing it and thus taking away any power it has.
And if by any chance you live in Alberta… consider moving to another city that embraces your lifestyle a bit more if you wish to reduce or eliminate the looks of disgust. Montreal’s just a bit too spicy in my opinion, but if spice is what you like, it has plenty for you. I can’t recommend Toronto as I detest the city, but it is the biggest, many lifestyles going on there. Ottawa, my city, is much calmer and a bit slower than Toronto or Vancouver, but has plenty of fun activities and is very welcoming.