Would begin proceedings to remove them. If you and the Defendant are not on good terms and the Defendant was aware that the proceedings were in progress, and that the order for sale was on its way, then the Defendant may have done this on purpose to thwart your sale or at least, to try to do so.
You need to decide what you want and then work out how you are going to get there while considering what is in the way.
You want the property empty.
The occupiers in the way so you need an order to get the occupier out.
The defendant put the occupier in so you need an order for the defendant to get the occupier out.
The defendant is in breach of the order the sale now but wasn’t at the time.
Ultimately all you need is the occupier out of the property.
Therefore I would submit all the applications, ask for them all to be heard together and let the court decide how it wants to progress it.
Enforcing the order for sale against the occupier is potentially an option but as you already have the order and she wasn’t party to those proceedings, you would need another set of proceedings because she would have to have the opportunity of defending them so I don’t think it’s an option.