She might leave me if I cant them to behave?

Have your girlfriend stand up and tell them point blank she won't put up with that attitude. You back her up and make sure they understand you are both done with it. There will be no more of it, period. If she might be in the picture for you long term let her deal with them or do it as a couple. If she's ping through, she still shouldn't be expected to put up with that treatment. Put them in bible cles or something where they will learn respect.