King Charles I certainly believed that women were involved in the fighting, for in 1643, he issued a proclamation forbidding women from dressing as men in order to fight.
Despite this measure, a small number of women do seem to have taken part in combat. One famous example is Jane Ingleby of Ripley Castle, who reputedly charged with the King’s cavalry at Marston Moor, while many other women travelled with the armies as camp followers.
Some aristocratic women took command at home while their husbands were away. Lady Brilliana Harley defended Brampton Bryan in Herefordshire against the Royalists, while Lady Mary Bankes famously held Corfe Castle for the King, withstanding two sieges. When the Parliamentarians tried to climb the walls, Lady Mary, her daughters and her female servants helped drive them off by raining hot coals and stones down upon their heads.
There is also plenty of evidence of women taking responsibility for the defence of towns and cities. Thousands helped dig the defences of London when it was feared the Royalists might attack the city at the end of 1642, and some 400 women helped defend Lyme by putting out fires, standing guard, reloading muskets and even shooting at the Royalist besiegers. When the Royalists temporarily withdrew, the women ran out with picks and shovels and levelled the enemy earthworks.