Footage of an attack on a chip shop worker by a Cardiff schoolgirl has attracted thousands of hits on video-sharing website YouTube.
An increase in violent crime among girls is hard to prove.
The 23-second clip shows the worker being attacked as cheering children look on.
Meanwhile, a 15-year-old girl from the same city has spoken of her "upset" after images of her being attacked by a classmate were also posted on the web.
She complained that the posting meant "everybody is going to know I'm a wimp".
Statistically, an increase in numbers of offences of violence and disorder involving girls is hard to prove.
But these are just two in a string of recent incidents committed by young females to make headlines.
Dr Sally Henry, a researcher from Brunel University, argues that images in the media are "feeding" aggression among girls.
And she believes the violence they become involved in is a kind of twisted feminism.
Dr Henry told the BBC News website: "It's not surprising these things are happening because girls are witnessing scenes on TV, in films and in music videos where it's not just men committing violence, but women too.
"These girls think physical violence empowers them. It is feeding their aggression and they are misinterpreting it as some kind of feminism."
Last year, 17-year-old Beatriz Martins-Paes was sent to prison for at least 14 years for stabbing Charlotte Polius, 15, to death at a party in east London.
Prosecutors were clear the case marked a watershed.
Lawyer Aftab Jafferjee said it "exposed a new and sinister development in our urban society - the carrying of knives by teenage girls".
In 2005, teenagers Natashia Jackman and Shanni Naylor were both attacked at school by female classmates.
Natashia was stabbed in the eye in Camberley, Surrey, by a girl that defence lawyers claimed was "unhappy" and "wanted to fit in".
Sheffield schoolgirl Shanni needed 30 stitches after she was slashed across the face with a razor blade by a 13-year-old pupil.
In February this year, a schoolgirl was sentenced for kicking a 12-year-old unconscious at a bus stop in Mill Hill, north London.
The judge said she was trying "to reinforce her aura as boss" in front of her gang.
Dr Henry said: "It's a bit like the Spice Girls' 'girl power' thing. Kicking and lashing out is seen as a way of empowering yourself, but it's not.
"And it's not a way of attracting boys either like some girls might think. Boys might find aggressive women in music videos attractive, but they don't want to take them home and marry them."
The number of women, and particularly young women, accused of crimes or serving time in prison in England and Wales is still tiny compared with the number of males.
In fact, overall, the female prison population fell by 2% between February 2006 and February 2007, although the number of girls aged 15 to 17 in custody increased slightly from 64 to 69.
In London, the number of girls aged 10 to 17 accused of possessing a knife or drugs fell in the last three years.
In 2004/5, 38 girls were caught with a knife compared with 25 in 2006/7.
Burglary and robbery by teenage girls has gone up though, from 558 in 2004/5 to 652 in 2006/7.
But a spokesman for the Metropolitan Police explained that apart from occasional cases of women or girls harbouring a male offender or looking after a gun for a male, there were very few instances of females actively involved in gang violence in London.
'Seen and not heard'
Hugh McKinney, from the National Family Campaign, believes violence among girls is indicative of a general breakdown in society.
"Respect for authority among all young people, and the ability of older generations to impose order on youngsters, seems to be at an all-time low," he said.
Dr Henry believes the issue runs around the meaning of female identity itself, and she points to schemes in the US which are aimed at helping girls understand that.
"You need to get to them at 10 and 11 years old to educate them about what it means to be a girl.
"They need to know that just because they don't have to be 'seen and not heard' anymore doesn't mean they should be aggressive."