But in bed, not sitting in front of a TV. The exact date she was last seen alive is not known.
May 2008 reports
This was first reported in Jutarnji List, "a daily newspaper published in Zagreb, Croatia", on 13th May 2008. The body is alleged to have been discovered two days previously. The article's titled translates to "She lay dead in the apartment for 35 years!" The article says her body was found in her bed in the apartment.
"Must be no longer than 35 years - said Mirko Horvatić, a neighbor who was in the eighth decade of life."
A 14th May report in Zagreb newspaper Metro Portal says
"Hedwig lived in the apartment above me, and the last time I saw her in 1963 when my son was two years old. ... [said] 85-year-old Katica Caric, the oldest resident of the building,
which[who] has recently been given to a nearby nursing home for the elderly".
There was a second report in Jutarrnji List a few days later on 15th May 2008. The author of the article appears to be Velibor Panić. A man by that name has a facebook profile saying that he was a reporter in 2008. Other names in the report show up in web-searches with consistent locations and professions.
These reports seem to have been picked up by Associated Press at the time and a version of the story has subsequently appeared in some English language news media at around that time.
Dates of last sighting and of death
The date of the last known sighting of the deceased woman depends on the memory of an 85 year old in a nursing home and of other people of similar age.
The two original reports give the time she lay undiscovered as 35 years and as more than 40 years - it seems to depend on which resident or other person the reporter spoke to on each occasion.
I don't read Croatian and Google's translation isn't clear enough to be sure but it may be that the last known sighting was in 1963 (45 years before 2008 reports) but there was other subsequent contact suggesting the reclusive woman didn't die at that time - it may be she communicated for a while by lowering messages in a basket from her apartment window.
It may not have been possible to identify the exact date (or year) of death.
Reasons for non-discovery
At the alleged time of death, the apartment was in communist Yugoslavia. At that time, property was state-owned. I don't know if gas and electricity to a building like this would have been metered individually per apartment in communist times - it may be plausible that it was not and that in the transition from communism this small (18 m²) apartment did not acquire a separate account with utility companies.
Essentially, the story is that the apartment in which she was found is very small and was the subject of a longstanding ownership dispute among the residents of the building. It seems that until this dispute was resolved, no-one had authority to enter the apartment.