Although its quicker to feed her when the food is mashed, if she has a lot of teeth i think its time for you to let her experience the different flavours and textures of food. You should offer her a spoon with every meal, my ds is learning how to scoop and stab now, he doesnt want me to feed him. Although your mum might not like the mess I think you need to tell her that you want to stop mashing the food now and want to encourage independent eating...good luck!