My thoughts aren’t nearly as important as yours on this issue! 😆 However, since you love your girlfriend but hate her tattoos, it’s completely fair for you to tell her you hate them, and you hope she won’t get any more. She may be surprised that you hate them, and stop getting them. Or, not.
That said, it’s her body, you’re not married, and if this is one of the ways she expresses herself, consider the ways you express yourself that she may not like, and see if there are trade offs here. If she absolutely hates your car, and you love it, that may be a trade off. Same goes for clothes or hair (some women hate beards, while the men who wear them love them). Maybe your best friend stinks up her apartment with cigars and beer every time he comes to visit, and that’s the trade off she makes for you putting up with her body art.
If you can find a way to be all right with her tattoos, then consider it one of her quirks that you could live without, while she’s not someone you could live without. However, if looking at the tattoos on her body repulses you, well, then you’ve got yourself a deal breaker. Don’t feel guilty. Do be honest.