I think something like this scenario might have taken place, and it would also explain why the jurors will be taken to see inside her apartment.
It's difficult to image what other scenario could have led to her death in such a short space of time. (She would surely have been in contact with someone by phone if she had not been killed fairly soon after arriving home.)
Originally, I thought perhaps he went round and suggested a friendly pre-Christmas drink (fairly normal behaviour) and then he made a pass, which she rejected. He, being drunk, persisted, and he ended up strangling her in a fit of rage. This now seems unlikely. I don't think he would have progressed to that stage so rapidly.
It could well be that he was in her flat when she got home. He knew that her boyfriend was away. Perhaps when she didn't arrive home at the usual time, he assumed that she had gone to spend the night somewhere else, and saw this as an opportunity to set something up, or simply to have a look inside her flat.