Apparently it comes from a report called "Lambrini Lady – the Lost Political Generation" produced by Steven Fielding - Nottingham University’s Professor of Political History and Director of the Centre for British Politics, School of Politics and International Relations. They are,
Young, female and feisty, Lambrini Lady, represents the millions of 18-34-year-old British women who have views but don't vote.... But despite their reluctance to take to the polls, these women are far from ignorant about policy. Busy raising pre-school or school-aged children, their concerns centre on family, health, crime - especially sentencing - and education.It does not say that they drink cheap shitty weak sparkling wine though.