If last week’s leaders’ debate taught the voters anything, it is that a new political sisterhood has taken shape. In the absence of David Cameron and Nick Clegg, it was the Scottish Nationalists, Greens and Plaid Cymru who grabbed the centre of the Westminster stage – and marked their closeness with a group hug when the BBC credits rolled.

Less fierce than Nicola Sturgeon, less shrill than Natalie Bennett, Leanne Wood has emerged from three-and-a-half hours of primetime television as the leader you’d most likely invite around for a cup of tea. Leader of Welsh Nationalist party Plaid Cymru since 2012, she is fine with the adulation that her valleys accent won on Twitter – as long as those who tuned in listened to her policies, too.

“I went on in order to give Wales a voice and I think I managed to achieve that,” she says. But behind the voice are stern principles. Her politics are to the left of Labour – “but that is not hard, is it really?” – and she was once expelled from the Welsh assembly for calling the Queen “Mrs Windsor”. “I believe that anyone should be able to aspire to be head of state. I don’t see why any barriers should be put in the way,” she tells me.

Wood also had no qualms about ticking off Nigel Farage for his claim that HIV-positive immigrants should not be allowed into Britain. Criticising the “style of politics where groups of potentially vulnerable people are scapegoated and bullied”, she says of Farage: “When I was given the opportunity to call him out, it was an opportunity I couldn’t resist.”

With polling day just 17 days away, the question now is how long the political sisterhood lasts. Plaid offered “solidarity and support” to the SNP during the referendum push last year, with many of its members holidaying in Scotland in August to help the campaign and pick up tips to take home. Together with the Greens, the three agree on plenty, such as scrapping the Trident nuclear defence and an end to austerity, but such is the SNP’s strength that it might not need the other two to force its way into a coalition government.

“We have said that we will co-operate together and it may well be that we take different positions after the election, but at the moment it makes sense for us to look at which ways we can co-operate for mutual interest,” says Wood, who counts Sturgeon as a friend.

Because most Welsh people get their news from London-based sources, Wood is on a whistle-stop media tour, meeting me in a noisy café around the corner from the BBC headquarters in between appearances on the Jeremy Vine Show on Radio 2 and Radio 1’s Live Lounge.

They are great bookings for the leader of a party that is only the third-largest in the Labour-controlled Welsh assembly and holds three seats at Westminster. Whether inside or outside government on 8 May, Plaid is looking to use this campaign as a springboard. “If we hold on to those [three seats] that would be great, but I am hoping we will see our best-ever election result in Westminster,” says the 43-year-old, sipping elderflower and soda. “Four has been the maximum before so I am very much hoping we can trump that.”

On her mind though, is how she can convert national interest into Welsh votes in the assembly elections next year. “The SNP had a breakthrough in 2007 when it formed a minority government and then went on to win enough support and trust to run a majority government in 2011. I want us in Wales to do the same.”

Wood was a break from the past for Plaid as the party’s first female and first non-Welsh speaking leader. She is learning. “I am not as good as I would like to be and I’m not as good as my 10-year old daughter, actually,” she confesses. She lives in the village of Penygraig in the Rhondda, having moved away for a few years before returning to the same street she grew up in “to ensure that my daughter was able to grow up in a proper community”.

It was this community, shaken by the miners’ strike, which shaped her political views. Her father was made redundant shortly after local pit closures. He wasn’t a miner; he worked for a buildings supply firm. But jobs in the wider economy disappeared because “disposable income just disappeared”.

She adds: “We still haven’t recovered from the blow that was delivered to us in the 1980s by the closure of the pits. We still struggle.”

Electronics corporations lured to Wales with regional grants were supposed to fill the jobs gap. In her student days, Wood worked on the production line at the Bosch factory near Llantrisant making car alternators. At its height, the plant employed hundreds – until the German company moved operations to Hungary. Later, working as a probation officer, she saw plenty of cases of substance abuse and teenage pregnancies associated with deprivation. So it is no surprise her policies involve self-help.

Plaid wants to fund 1,000 extra doctors, at a cost of £65m, in part with a new tax on sugary drinks, as well as award public contracts to more Welsh companies. Setting up a new national energy company would let people bulk-buy gas and electricity. By increasing the minimum wage to the living wage for more than 250,000 workers, she thinks Wales can cut its in-work benefits bill. Securing an extra £1.2bn from the Treasury to give Wales parity with Scotland is a “key priority”.

Should Plaid gain a share of power, there are policies here that Wood argues would benefit the whole of the UK. The fact the Scottish economy is far stronger than the Welsh one is the reason why she won’t be pressing for her own referendum immediately.

“We are at different stages of our journey in terms of devolution. I think most people in Wales would want to see improvements in our economy before being able to contemplate voting yes in a referendum on independence. If we can demonstrate that we can make a fair fist of running our own affairs and move towards a more self-sufficient model, then more people I think will get behind the project for independence.”

The CV

Personal: Lives with her long-term partner and her 10-year old daughter, Cerys.

Education: Studied at Tonypandy Comprehensive School, and the University of Glamorgan.

Career so far: Worked as a probation officer in Mid Glamorgan; support worker for Cwm Cynon Women’s Aid from 2001; lectured on social policy at Cardiff University. Elected as a Member of the National Assembly for Wales in 2003. Became shadow social justice minister from 2003 and elected leader of Plaid Cymru in 2012.