Caroline Lea, 36, from Blackpool, denied charges involving two 15-year-old boys, including an allegation of having a threesome.
She was found not guilty at Preston Crown Court of seven counts of engaging in sexual activity with a child.
She was also cleared of supplying amphetamines but was found guilty of one count of allowing her home to be used for smoking cannabis.
The prosecution claimed she allowed boys to smoke cannabis and drink alcohol at her Clifton Drive home.
She told the court she had developed an alcohol problem after she lost her job at the Department For Work and Pensions (DWP) because of depression.
She accepted male youths congregated at her house but said she would regularly ask them to leave.
She previously told the court she was "soul destroyed" when she was arrested and had "no idea" why the three boys made allegations against her.
Lea will be sentenced for the drug charge on 25 February.
A mother-of-three accused of having sex with underage boys has been cleared.