The actress's character Lauren Branning has used booze to ease her pain since her mother Tanya (Jo Joyner) was diagnosed with cancer last year.
Although Tanya has since been given the all-clear, Lauren's wild behaviour is expected to continue for some time to come.
Jossa told The Sun: "The story has completely changed the way I think about alcohol. Before we got started, my mum filmed me when I was drunk and showed me the video afterwards. It was disgusting.
"That helped with research, though. I haven't drunk any alcohol for about six weeks, so it's definitely affecting me."
The 19-year-old added that she tries to get dizzy on set before filming scenes which show Lauren drunk.
"The best way to prepare is spin around loads," she said.
Jossa won the 'Most Popular Newcomer' prize at the National Television Awards in January.
> EastEnders' Jacqueline Jossa: 'I ignored Tony Discipline attention'
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> Read more EastEnders spoilers and news
Watch Lauren's EastEnders character trail in the video below: