I don't know that it is really something you can control. Your best bet is to either avoid it (as in you don't go with that person out to eat) or to ignore it. Those are your two choices. If you are in a relationship with someone with bad table manners or dating someone with bad table manners then obviously you can't avoid it. Your best bet in that situation is to ignore it. Try not to look, try not to pay attention. Distract yourself from it. You could always talk to the person about it but I don't know how well someone would perceive you coming to them about their table manners. Other than that I really don't know what to tell you. Best of luck!