This is Dr. David
TSH level of 2.58 is normal and could mean her thyroid levels are completely normal
T4 have the shortest 1/2 life in the body an can fluctuate the most
so high or low levels of T4 once in a while is not a worry.
that is good she is seeing an endocrinologist.
but I don't know why her doctors are saying she has overactive thyroid function.
that would cause the TSH levels to be less than 0.3
has her TSH levels been low before?