Karlene Muschette slashed the woman's face and back and struck her on the head at a beach-themed party at the Dog and Partridge pub in Bilston.
A gun was also fired when what was supposed to be a family-friendly party turned violent at the Broad Street pub in July 2019.
Footage posted on social media showed a fight starting inside the pub during the pool party before trouble spilled outside.
Muschette and her 34-year-old victim are believed to have been involved in an online feud for some time before the party, West Midlands Police said.
An argument then broke out between two groups following a row between Muschette and the woman.
Initially ice and water bottles were thrown before the situation escalated and Muschette ran towards the woman who shouted ‘leave me alone’ before using a meat cleaver to slash her across the face and again on her back.
The woman tried to fight back but Muschette struck her head, resulting in her skull being fractured.
Muschette claimed the attack was in response to ongoing harassment over social media.
The 38-year-old, of Hartill Street, Willenhall, was found guilty of wounding and sentenced to nine years behind bars at Wolverhampton Crown Court on Friday.
Meanwhile the pub was forced to close after the brawl, before the landlord voluntarily surrendered his licence.
Wolverhampton Council said at the time that the pub had held the event despite previously being denied a licence for a family fun day and barbecue.
Detective Constable Craig Bathgate, from West Midlands Police CID, said: “This was a complex investigation which involved multiple witness accounts and historical allegations.
“However forensic evidence and extensive investigations have ensured that Muschette has been brought to justice for this brutal attack which could have resulted in far worse, and even fatal, injuries. It is right that she has received a significant sentence for her actions."