When is blood sugar too low for a 12 year old girl who is not a diabetic is and....is 95 too low in afternoon?

No. A value of 95 is within normal. A blood sugar less than 60 would be concerning. If someone had a blood sugar less than 60 consistently and/or had systemic symptoms such as near passing out, dizziness etc then you should ask yourself why is this happening and consider and endocrinology consult.
No. Blood glucose levels largely depend upon their timing with the last meal/snack or beverage consumed. A BS level of 95 falls within the fasting range for non diabetics, and may not be considered "too low" if separated by a meal for several hours. To address ongoing concerns, the child would need closer monitoring of BS levels, an evaluation by the physician for additional info. and testing.