The cabinet office is in the same building as the flat. The rules didn't specify that the person carrying out the work had to remain in one room!
Any tradesperson with half a brain would realise that keeping well away from other people in the household they were working in was a good idea.
Did Lytle ensure she was two metres away from anyone else the whole time she was in the cabinet room as per Robert Jenrick's advice at the time:
“Work carried out in people’s homes, for example by tradespeople carrying out repairs and maintenance, can continue, provided that the tradesperson is well and has no symptoms.
“Again, it will be important to ensure that Public Health England guidelines, including maintaining a two-metre distance from any household occupants, are followed to ensure everyone’s safety."