Breakdown of Omdat de astroloog dat element heeft gekozen, is ze blij.
zijn
to be
blij
happy
hebben
to have
dat
that (het-words)
Questions & Answers about Omdat de astroloog dat element heeft gekozen, is ze blij.
Why is it heeft gekozen here, and could I also say gekozen heeft?
Yes, you can use either! Because omdat starts a subordinate clause, the verbs are pushed to the end. When you have a helping verb (heeft) and a past participle (gekozen), you can put the helping verb first (heeft gekozen, known as the "red" word order) or the past participle first (gekozen heeft, the "green" word order). Both are completely correct and mean the exact same thing.
Why does the second part say is ze blij instead of ze is blij?
This is the classic Verb-Second (V2) rule in action. The entire first chunk of the sentence (Omdat de astroloog dat element heeft gekozen) counts as the first position. The main verb of the sentence (is) must be in the second position, so the subject (ze) has to swap places and come right after it.
Why do we use dat for "that element" instead of die?
Because element is a het-word (het element). When pointing out a specific het-word ("that" or "this"), you must use dat or dit. If it were a de-word, you would use die or deze.
Does ze refer to the astrologer here?