Answer: her IQ level would be 95 which most 13 year old girls should have around an IQ of 100-105 since her mental age is that of a 12 year old she would be within the The Concrete Operational Stage which is what category on the "piaget's 4 stages of cognitive decision making scale"
Step-by-step explanation:
Seeing that she is at least a year behind in her mental development she would have The Concrete Operational Stage which is where children begin to thinking logically about concrete events
They begin to understand the concept of conservation; that the amount of liquid in a short, wide cup is equal to that in a tall, skinny glass, for example
Their thinking becomes more logical and organized, but still very concrete
they begin using inductive logic, or reasoning from specific information to a general principle. She should be able to understand basic events and point out most differences in everyday objects/words.