gas safety problems and penalties

Other

My rental flat is in a London conversion with 5 floors and I have a gas fire and boiler. My gas safety was up to date. A neighbour had work done and rubble came down the chimney. It took me months to get the managing agents for the block to have a contractor test my gas fire for safety, he also did a smoke test on the chimney but did not issue the actual gas safety cert. Two months later the safety cert. expired (in March) but i was still trying to get the managing agents to confirm that the communal flue was safe so i delayed having my own check done. I felt that the communal flue, damaged by the neighbour was their responsibility, not mine. that is an on-going problem and something I would like advice on. The URGENT problem however, is that my tenant, who has now left is threatening me over not getting the safety check done. She doesn't want to pay the dilapidations from her EOT report. She is making up stories about her child suffering from headaches etc. What is my position, how much damage can she do and what would be the worst scenario for me if she pursues this action. I am losing sleep over this and would appreciate a reply asap. Many thanks Carol