Take a look at the sentence again:
Sparkling with jewelry conned from ex-boyfriends,
Sylvia keeps an eye out for new victims with fat wallets, she still
needs a pair of diamond earrings to complement a necklace that she managed
to coerce Ricardo into buying.
The comma between ex-boyfriends and Sylvia is correct. Sparkling with jewelry conned from ex-boyfriends is a present participle phrase. A present participle phrase will begin with an ing word like sparkling. Sylvia keeps an eye out for new victims with fat wallets is a main clause. When a present participle phrase introduces a main clause, you need a comma to separate them.
Go back to the sentence to try again.