Valerie Graves was found dead in the property in Smuggler's Lane on Monday morning. She had been house-sitting with three other members of her family over Christmas while the owners of the home were on holiday.
Sussex Police are continuing to appeal for witnesses to come forward, and investigations are continuing. Detective Chief Inspector Jon Fanner said:
"The post-mortem has revealed the cause of death but we are still keeping an open mind as to the motive. We are appealing for witnesses who may have seen anyone acting suspiciously or anything unusual in the area from late afternoon on Sunday 29 December to around 10am on Monday 30 December.
"Please call us if you know anything, no matter how insignificant you might think it is. It could be important to the investigation."
A police officer from the force overseeing major anti-fracking protests has received "management advice" after labelling activists as "scum" on Twitter.
The comment was picked up by a member of the public, who tweeted, "#balcombe @sussex_police should your officers really be calling protesters 'scum' on twitter? I suggest you issue some guidance ASAP."
The force said in a statement: "Sussex Police has received a report of a personal Twitter account belonging to a Sussex officer, which is abusive to protesters at Balcombe.
"We have worked hard to engage with everyone involved in and affected by the activities surrounding the drilling operation at Balcombe and no matter who authors them, such comments are unhelpful and not acceptable."