What Causes Vomiting While On Amoxicillin?

Why is amoxicillin making my 2 year old granddaughter throw misbehave to the point of violence. She changes moods on a dime. uses force to try to make people do what she wants yet she doesn t have any idea what she really wants. Pinching clawing biting and hitting have become uncontrollable. her efforts to communicate are gone even though she has a very large vocabulary. With potty training she would get up every morning and come to me to pee pee. she stopped wetting her pull up two weeks ago. Now she hasn t pottied at all on the potty since she started this medication. Please help.