Careless or neglect?!

LO, 2-1/2 years old. She was over at her grandparents for the last couple of days. We, had to go out of town. MIL told me they were going out for a walk in the afternoon.

We picked her up this evening. Her diaper was extremely full, she had tights under her jeans on that were riding low and her long sleeved shirt wasn’t tucked in-exposing tummy/back.

Her cousin who had Covid and meningitis last week was over yesterday and today.

Now we are home, my LO is sneezing, runny nose, low grade fever and tummy ache, who isn’t settling so well to sleep.

She could’ve gotten a cold from the afternoon walk or could be the beginning of meningitis. I’m a bit angry that my MIL didn’t bother to change her diaper at least. LO looked sloppy and neglected there. Kids get sick but is it also a bit careless or am I overreacting here?