The 19-year-old fell ill in a flat in Renfrew at 10.15pm on Sunday and was rushed to Paisley's Royal Alexandra Hospital (RAH) where she later died.
Four other people were also taken to hospital from the property in the town's Paisley Road to be treated for signs of suspected drug misuse.
Two other women, aged 18 and 19, and two men, aged 24 and 31, were taken to the Southern General Hospital in Glasgow and RAH.
Neighbours spoke of their shock. One woman said: "I can't believe it. I just don't want to live here anymore. It's getting worse.
"I can't believe someone has died, it's horrible. This needs to stop."
A post-mortem examination will take place to determine the exact cause of the woman's death, with witnesses believing she may have also taken ketamine.
Mephedrone, which has the street name MCAT, is sold as a white powder - which users snort in a similar way to cocaine - or capsule form.
Detective Chief Inspector Arlene Smith said: "Extensive inquiries are continuing into the circumstances of the woman's death, and although unconfirmed, one of the lines of enquiry is that prior to her taking unwell she may have taken an illegal substance.
"At this time it may be that the drug involved is MCAT.
"Police Scotland is issuing a warning to anyone who has obtained or taken this or similar substances. Do not take illicit drugs and stay away from any unknown substances. No-one can predict the risks involved or the serious consequences."
Medical staff are also urging anyone who may have taken the substance and are feeling unwell to visit accident and emergency.
In February, 17-year-old schoolgirl Regane MacColl died after apparently taking a Mortal Kombat ecstasy tablet.
She died after falling ill in The Arches nightclub in Glasgow.