In the article, we are told she moved into "a dilapidated house".
Then, we see "she bought the five-room house".
This follows the a/the rule perfectly.
I bought a house. The house is small.
The rule is that if you mention a something, the next mention of it will be with a the.
"He has a very fast car. But the car sits in the garage and he never drives it."
The first mention of an object, person or idea is often indeterminate and takes a and as soon as it becomes specific the second mention you mention it, it takes the.
This is one of the simplest rules about a/the.
And if you have a thing that has become specific with definite article the, the other specific things associated with it are also specific.
I bought a house yesterday. The house and the garage were painted purple.
There is only one house and one garage. The house didn't have just any garage, a garage. It was the garage that was associated with the house.