I still fully support my ex wife. My gf says i should sever all ties

my gf and I have been together for 8 years and she gets upset when ever i give my ex money, i fully support my ex financialy. the way i see it, we were married 25 years and she never had a real job. She was a stay at home mom. I, on the other hand, had a career and am doing well. She gave up any chance of a career to be at home with our kids and I feel I owe it to her to continue supporting her as I did for our 25 years together. My gf believes i should stop all support. Thanks for your input