Have you caused damage?
Has she let you in to do any repairs?
Are you prepared to sue?
Are you willing to sue her?
Has she paid you for the work?
Was there a a separate price agreed for that other work?
No, but did you agree anything verbally?
Yes but did you agree a price?
OK. You do have a contract with her over those matters. It might not be reduced to writing but one exists and you are entitled to be paid the value of the job.
There are a number of issues here.
Dealing with her claim against you, if she can show that the work was done to an inadequate standard then she has a claim for the cost of repair. However, that would be reduced to reflect to the fact that she didn't allow you access to the property to put this right.
She may have a claim for a refund of something because you didn't complete. You are entitled to charge for the value of the job that you did and any additional expenses but couldn't keep the full amount if you hadn't finished.
However, your only real options are either to pay her off and get rid of her or invite her to sue and deal with it at court if she does. Probably she won't but you need to be alive to the fact that she might.
If she does then just raises these defences and claim for the additional work.
Can I clarify anything for you?
Well, as I said above really. That criteria would need to be met before she would have a claim.
All the best.