She was pronounced dead on May 23 in Fenton, and four people have since been arrested.
A woman, 30, was arrested on suspicion of administering a noxious substance.
The other three, two men and a woman, were arrested on suspicion of being concerned in the supply of drugs.
They have been released under investigation.
This is a breaking news story and is constantly being updated.
Please refresh the page regularly to get the latest updates.
Reporters working on dailystar.co.uk will be working to source the latest information, reaction, pictures and video related to this story.
You can also follow us on Twitter @Daily_Star to get the latest news updates 24 hours a day.
Or download the Daily Star app for flash alerts on the biggest stories of the day.