The Clueless star passed away in 2009 after suffering a cardiac arrest linked to pneumonia and anaemia, while Murphy's husband Simon Monjack died five months later from the same ailment.
Now the actress' mum Sharon is claiming toxic mould killed the couple and is blaming the builders of the property for causing the deaths.
Sharon Murphy has now filed a lawsuit against her former lawyers for legal malpractice, claiming they duped her into agreeing to a settlement and giving up her rights to sue the property builders.
She alleges the attorneys convinced her to accept a settlement over the construction problems in January (11), but failed to explain to her that she would then be unable to take action against the builders.
TMZ.com claims she is seeking the amount she would have won in a wrongful death lawsuit, as well as other damages.