If you didn’t have a new address,then the last known address (the property) is good for service. The court assumes that will have their mail forwarded. However, if she makes an application to set aside the possession order, the court will have to hear it and you will have to defend it.
I can’t understand why she is applying to set aside the order if she has already moved out.
Obviously, we have no idea what she is counter claiming until she issues her counterclaim which could before anything, lack of repairs, compensation for failure to protect deposit, a whole load of different things including things that she may allege which are not actually true and you would have to defend.
If part of your claim was for rent which she had not paid, she will also struggle to prove that she has paid the rent if she hasn’t.
Can I clarify anything for you?
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We can still exchange emails.