Here is the sentence again:
The comma between wallets and she causes a comma splice. At this spot, there are two complete sentences joined with just a comma. Such a construction is a major writing error. Sylvia keeps an eye out for new victims with fat wallets is one complete sentence. She still needs a pair of diamond earrings ... begins the next complete sentence.
To fix this problem, you could put a period after wallets and capitalize the S for she.