I check something like 7 to 10 times a day. First thing, after breakfast, before lunch after lunch, etc. I also test in between meals sometimes if I'm going to go for a walk or something similar.
I think her fingers will gradually get used to it. Use the sides of the fingers rather than the 'pad', use a finger pricker on the lowest setting you can that will still slow you to get enough blood. Also, maybe wash her little hands in warm water before as it can help getting the blood to flow easily.
Could you have a favourite cuddly toy and pretend that the toy has blood tests too? Or maybe a reward chart with stickers for being brave?