I'm speaking from a breastfeeding point of view, but even with formula, eating solids is for the EXPERIENCE at this age. And if y'all force her to eat, what is her experience like? Not a very positive one. Just try the same things several times in a row (they say it can take MANY times before a child accepts a new food).
Also, my children hated baby food. Niether one of them "ate" until they could feed themselves. I delayed solids (didn't start with the first until 7 months, and the second was after 8 months), so mine were old enough for soft finger foods. Your granddaughter is as well. I started with avocado, as it's sweeter like breastmilk. Very well cooked and soft carrots, avocados, bananas, sweet potatoes, green beans.....if they are well cooked and soft, but diced small, she can pick them up herself. At 8 months she probably just wants the independence of self-feeding.
My children were both started on solids later (son was 7 months, daughter 8.5), yet neither one of them really ate until later. Son was 10 months old before he enjoyed food, and daughter was 11.5 (2 weeks from her first birthday) before either of them ate much more than a bite or two. THey were happily breastfed (and both continued breastfeeding well into their second year, self weaning when they were ready) and their weight was adequate. In fact, my first son was 20 lbs at 6 months old from breastmilk alone!
But remember, for the first year, breastmilk or formula is the main source of calories. Solids are for the experience of eating. Don't stress but offer her healthy finger foods.