Should I stop pumping?

Hi wanna seek some opinions on breastfeeding. Currently my girl is 18 months and she has been exclusively drinking only bm so far. Recently she suddenly decide that she doesn't want todrink expressed bm anymore when I'm at work but she still is eager when I latch her. I tried to use the ebm to make chocolate milk w honey for her but she still doesn't want. So no choice give her fresh cow milk which she takes very well. Should I stop pumping at work since she doesn't take ebm anymore? I am apprehensive of my milk supply dropping especially as I still want to have enuf supply during the weekend to latch her. But I see the packets n bottles of ebm lying there I feel very stressed because I will feel that it's very wasted to just dump. Opinions on whether should I stop pumping altogether?