Hold on there, cowboy. You know how dinner and dessert are two different things? Well, sex and masturbation work the same way. Sex is about romance, intimacy, and exploration. Masturbation is about getting off. Now, if your girlfriend is choosing to masturbate instead of having sex with you, then, yeah, that’s a problem. But if she still touches herself or uses a vibrator when you’re not around, I’d just chalk that up to your being unavailable.