Sarah S. answered 05/19/19
Fluent German Speaker with Immersion and Tutoring Experience
Hello! I am not sure what the sentence was supposed to be, since it seems to have added some strange characters. If it was supposed to be: Sie fuhr mit der ihr eigentlichen, drolligen Aufmerksamkeit - that translated without context would be something like "She drove with her odd, comical attention"
As for "mit ihr der" - the preposition "mit" meaning with in English is a dative preposition. That means that you must conjugate the noun that "mit" is referring to into the dative case. Because the subject of this sentence (SIE) matches the noun that the subject is with (MIT) you use the "mit ihr der" format. If the subject of the sentence was someone else then you would simply use "mit ihr"
Example:
I am with him = Ich bin mit ihm
He is which himself = Er ist mit der ihm