The first form.
I am AS good as she IS (good is implied).
I work AS attentively as she DOES (works is implied).
From grammarbook.com:
To decide whether to use the subject or object pronoun after the words than or as, mentally complete the sentence.
Examples:
Tranh is as smart as she/her.
If we mentally complete the sentence, we would say, "Tranh is as smart as she is." Therefore, she is the correct answer.
Zoe is taller than I/me.
Mentally completing the sentence, we have, "Zoe is taller than I am."
Daniel would rather talk to her than I/me.
We can mentally complete this sentence in two ways: "Daniel would rather talk to her than to me." OR "Daniel would rather talk to her than I would." As you can see, the meaning will change depending on the pronoun you choose.
