Should I break up with my girlfriend by phone?

Do it. You're going to have to stay firm in your decision. It can be hard to hurt someone's feeling but as a man, you would be a coward not to.

Talk to her in private but not at home or anywhere where you would have to share a ride home or walk in the same direction (this is to allow you the opportunity to leave when it's over and not have to kick her out or prolong the issue). When you do it be firm and extinguish any hope of the relationship (dont tell her "if things were different..."). She might tell you that she'll change but if you made up your mind tell her you are not willing to give her another chance. If she rages at you, let her blow off some steam (unless she gets physical in which case leave IMMEDIATELY).

Just remember that while you should try not to be a jerk, also don't be too kind as that will only give her hope and hurt her more. Stand firm, man and get it over with. It's going to suck, expect the worst but you'll get through it. Just know it might not end with just that.

hope this helps

It is totally fine to break up with her if that is what you want to do, but show her the respect to do it in person, not by phone.

Go for it. It will save the awkwardness

rape her