I Have A New Step Granddaughter Who Is Very Forgetful

I have a new step granddaughter who is very forgetful to the point that she can't remember pets that have been in the household for years. SHe can't remember what she had for dinner; says that she hasn't eaten, what was said an hour again and the list goes on
One worrisome thing is that her mother feeds her very little with lunch being spinach and tuna (no bread, no mayo, etc). She also lives on a "farm" where her step sisters have had Lyme Disease after a tick bite.