So who are the other six?
Carolyn McCall joined the budget airline from Guardian Media Group in 2010.  She was made a Dame in the New Year Honours list this year for her work in the aviation industry. Under her, the company entered the FTSE 100 for the first time.
Profits at the airline rose for five years in a row and last September it made a record £681m. This year, however, has been more turbulent, with the company posting a half-year loss of £24m, hurt by the fall in the pound.
Veronique Laury was considered a surprise choice to head the home improvement chain when she took over from Ian Cheshire in December 2014. She had been at the business 11 years and led the French DIY chain Castorama.
According to an interview in the Financial Times, she has renovated at least two houses and is a keen gardener and painter.
Liv Garfield was just 38 when she became chief executive of the water firm Severn Trent in 2014. Before that she was head of BT Openreach, where, according to her online biography, she spearheaded and oversaw the commercial roll-out of fibre broadband to two thirds of the country.
Alison Cooper has been head of the Bristol-based cigarette firm Imperial Brands for more than six years, having first joined in 1999.
Last year she oversaw a $7.1bn expansion into the US with the purchase of brands including Winston, Maverick, Kool, Salem and e-cigarette brand blu. According to an interview in the Evening Standard, she is a cigar smoker and also a keen singer.
Moya Greene was named as chief executive of Royal Mail in 2010 - coming from the top job at Canada Post. She oversaw the company's £3.3bn privatisation in 2013 and has been described as "relentless, a force of nature, a tough lady".
She'll need that to help get Royal Mail back on track - earlier this year it reported a 33% fall in annual profits as it faces increasing competition.
Alison joined Whitbread - owner of Premier Inns and Costa Coffee - in January this year, having forged her career in banking - most recently at from Lloyds Banking Group, where she was head of their retail division.
She told the Daily Mail earlier this year that she stays in Premier Inns when she travels and that "we are definitely short of female CEOs. Clearly there is work to do there".

The deal to stop fighting was agreed between the Syrian government and some rebel groups fighting against them.
There has been a war in Syria since 2011 and since then, it's thought 300,000 people have lost their lives.
Four million people, including children, have been forced to leave the country and seek safety in nearby countries and Europe.
So far, the new ceasefire, which started at midnight on Thursday, seems to be holding, although there have been reports of isolated fighting in some areas.
Read our guide to find out more about why there is a war in Syria and why the city of Aleppo is so important.
A ceasefire is an agreement by opposing sides to stop fighting in a war.
This can be for a certain amount of time as a short break or it can be agreed for a longer period of time.
In this ceasefire in Syria, there are many groups involved.
Syrian government forces, the Free Syrian Army and many rebel groups have all agreed to the ceasefire.
But not all groups operating in the country are part of the deal.
The group that calls itself Islamic State and other extremist Islamist groups, are not part of the ceasefire.
Islamic State have taken over large parts of Syria and neighbouring Iraq and fighting against them is continuing, whilst the ceasefire is underway.
If the ceasefire does continue to hold, then peace talks aimed at ending the war in Syria could be held within a month.
GSK has just announced Emma Walmsley will be its next chief executive taking the total of women running FTSE 100 companies to seven.
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A new ceasefire is underway in the war torn country of Syria in the Middle East.