I broke my diet because of my mom's desserts

My mom keeps bringing homemade sweets on a tray. Even when I say I'm on a diet, she doesn't believe me and says, "You were picky when you were young, it worried me." To be honest, I can't say no to her, but I also get really frustrated with myself. What can I do to find a solution? Is there a way to stay away from sweets without upsetting my mom?