Query Re-Set Off of Arrears

We have a tenant who is being evicted for non payment of rent . She is claiming "set-off" of arrears because her boiler broke down in July . We didn't get her text message because she sent it to us on a phone that she had previously told us had been stolen so , as is our policy, we deleted her number awaiting confirmation of a new one. (Our phone rejects texts from numbers not logged in our system or we would be swamped with unwanted calls. )

She didn't write and she didn't phone the landline . However, she continued to live in her flat and when we tried to make arrangements to repair her boiler, she deliberately delayed the repair for two weeks .

When we repaired the boiler which was in fact , a blown fuse, it was clear that the socket had been tampered with - we suspect she did it herself .

Am I correct in stating that because she wouldn't let us in to repair the boiler, set-off is invalid ?