This just reminded me of our daughter. Mandi, the misses, didn't see eye to eye at all with Samantha to the point they were hating being in the same room. Daughter was around the age of 4 and was so much fun with me which prob made it worse for Mandi.
I gave up work and Mandi went back. Worked really well in the end because she now earns more than me and I'm back to full time too.
They're now very close.
As for the eating, our three were all fussy but she was the worst by far. Don't remember us letting them go hungry until much older.