DD2 is 2 months old and EBF, I've been trying to give DD1 (3 y.o) plenty of attention, positive reinforcement, reward charts and make a point to do an activity with her during baby's long nap but every now and then, without warning she'll pull baby's head away when I'm nursing, despite the fact that I've explained what I'm doing and that baby is having milk. I talk to her whilst feeding, sometimes we have a cuddle and a story, I'm at my wits' end. Today I tried to physically block her but she managed to lunge in and do it so quickly that she's scratched baby's head. And then she says "baby's crying" whilst looking concerned. I need help, I don't want to give up BF.