... Or she'll make mincemeat of you - hee hee.
That's something Avril Lavigne's mate discovered too late when he picked a play fight with her recently.
Yup, Avril may be a petite blonde and her pal a bulky bloke, but that didn't stop her showing him who's boss as the two wrestled in the sands of St Tropez.
Leaping on him with the full force of her slightly-built frame, the 24-year-old star soon had her friend pinned to the ground, flailing helplessly as he tried to regain control.
Some sources say the guy in question is Brandon Davis - Mischa Barton and Paris Hilton's ex - who has accompanied Avril to the French Riviera while her husband Deryck Whibley is on tour with his punk band Sum 41.
However, we're not convinced of the likeness.
What is clear is that whoever this fella is, he'll think twice before wrestling with Av again.
She's clearly not a lady to be fooled with, despite her diminutive status.
Check out more celeb pals on the beach in our gallery below.
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