Question about vegetarianism/veganism?

Ok so I've been a vegetarian for 6 months and a vegan for well a week, but yeah so my mom was like, "What difference do you make, it's not like they actually kill less animals because of you, they still are killing just as many." I didn't know what to say to her because I mean I went vegetarian because I personally don't want to eat dead animals, but yeah is there anything I can say to my mom to prove her wrong? I mean to be honest when she said that it almost made my efforts seem well pointless and ineffective even though I know that's not true. Thanks :)