Breakdown of Jag tycker att temat är intressant, och det gör hon också.
jag
I
vara
to be
hon
she
det
it (neuter)
Questions & Answers about Jag tycker att temat är intressant, och det gör hon också.
Why is det used in the second clause (och det gör hon också)?
This det is a pro-predicative. It acts as a pronoun for the entire idea from the first clause (tycker att temat är intressant). While English simply says "she does too", Swedish requires a placeholder object for the substitute verb gör. You are essentially saying "and that does she too".
Why is the word order det gör hon instead of och hon gör det också?
You can actually say och hon gör det också, but moving det to the front is a very common way to strongly connect it to the previous statement. When you place det at the front of the clause, the V2 (verb-second) rule applies, forcing the verb gör to come before the subject hon.
Why do we use gör here when the first verb was tycker?
Just like in English, Swedish uses göra (to do) as a substitute verb so you do not have to repeat the main verb. It replaces the entire action of thinking the theme is interesting.
Can I just leave out the verb and say och hon också?
If you use the conjunction och, you generally need a complete clause with a verb. You could drop the och entirely and just say hon också (she as well) as a short tag, but och det gör hon också is the standard, complete way to express this.