Chicago woman steals $50,000 over two year period from identity theft victim

From the http://www.dailyherald.com/ -

"A 30-year-old Chicago woman was behind bars Monday facing 20 felony charges alleging she stole more than $50,000 from a McHenry County man during a two-year identity theft scam.

Luevell Tracie Chester, of the 500 block of East 51st Street, faces six counts of aggravated identity theft, 13 counts of theft and a single count of financial institution fraud stemming from claims she gained access to the victim's checking account and drained it to pay for a mortgage, mobile telephone and credit card bills.

She was arrested last week by Chicago police and the U.S. Marshals Great Lakes Regional Fugitive Apprehension Task Force, then taken to the McHenry County jail Saturday.
Her arrest ended a nine-month investigation that began when the victim discovered about $51,000 missing from his checking account. The investigation determined that from June 2006 until November 2008 funds were electronically transferred from the account to pay off Chester's debts, McHenry County Sheriff's police said. 

Investigators are still looking into how, and why, the Harvard-area man was targeted.
'The victim has no idea who she is,' McHenry County Sheriff's Lt. Andrew Zinke said.
Chester, who is being held on $200,000 bond, could face up to 15 years in prison if convicted of the most serious identity theft charges. She is scheduled to appear in court Thursday."

What I don't understand is how someone doesn't notice $51,000 missing from their checking account for over two years?