She took to social media earlier today to write in a heated Tweet: "Bigger oops. [Mr Varadkar] won’t stand up for abortion rights. Also, yr (you're) a liar.”
Nancy then added that she hoped he enjoyed the "free concert and taco"!
It is one of the bizarrest cases of handbags at dawn stuff seen in a long time in rock 'n' roll. It all started earlier this weekend when the band's guitarist, Al Doyle waded into the Repeal debate with a tweet about An Taoiseach, describing him as a "tosser".
The Taoiseach had attended the band’s Olympia show with fellow Fine Gael members, including Minister for Finance Paschal Donohoe and Minister of State for European Affairs Helen McEntee.
However, some of the band were less than impressed when Leo and Co went backstage to say hello after the gig.
“Irish PM Leo Varadkar came backstage,” Doyle tweeted. “Wore a ‘repeal’ tote bag around my neck in front of him; he walked away. Tosser.”
Doyle then followed up with a series of what felt like semi-apologetic tweets.
It's being claimed that Nancy had a brief conversation with Leo and "took him to task" over abortion laws in Ireland.
Doyle later tweeted: "Nancy totally fucken took him to task as well, it was uncomfortable and awesome."
The Irish Mail on Sunday and the Sunday Independent ran front page stories about the backstage episode this morning.
The Irish Mail on Sunday (IMOS) claimed that Leo was "left red-faced" by the episode which they described as a "heated exchange" with members of LCD Soundsystem.
But sources close to the Taoiseach tried to play down the suggestion that there was any type of backstage spat.
"The Taoiseach was invited backstage in a private capacity," a spokesperson told IMOS.
"He was very happy to discuss the Eighth Amendment with a member of the band, and declined an offer of a photograph.
"The Taoiseach has already made his views knowns about the Eighth Amendment including its impact on medical practitioners.
"The government has now set an inductive date for holding the referendum and work is on schedule."
While Leo himself is reported as telling the Sindo: "One or two of the band members wanted to share their view with me on the Eighth Amendment. I had no problem at all with that."
But obvious something in this morning's reports prompted Nancy Whang to launch her astonishing attack on Leo and call him a "liar".
She also retweeted the front page of the Irish Mail on Sunday with its large headline: "How US Rock Band Ruined Night For Leo."
The IMOS also added that the spokesperson "refused to say" if the tickets were free.
But Nancy seemed to clear that up with her Tweet about how she hoped Leo "enjoyed" the "free concert and taco".
The Irish Mail on Sunday's Political Editor John Lee responded to Nancy's Tweet, saying: "Thanks for clearing up where the tickets came from Nancy. Irish Government refused to answer."
While in a front page story in this morning's Sunday Independent, Brendan O'Connor wrote that this bizarre handbags at dawn story is "possibly the end of Leo in the eyes of anyone under 40". He also wrote that it's "funny".
Junior Minister Helen McEntee waded into the heated Twitter exchange to defend her boss, rightly pointing out that it is actually Leo's government planning a referendum on the Eighth Amendment.
Brendan O'Connor said in his front page opinion piece: "Irish electronic act Le Galaxie perhaps summed up the feelings of many people when they responded to Helen McEntee on Twitter saying, 'Go fuck yourself.'"

Bigger oops, @campaignforleo won't stand up for #reproductiverights.?Also, yr a liar. Hope u enjoyed yr free concert and taco. #repealthe8th https://t.co/tPCgzs9VyM

— nancy whang (@nancywhang) October 1, 2017

Ok just got back to this after a very, very late night in Dublin.

A *very* late night.

Anyway, I realise some apologies are in order...

— al doyle (@aldoyletweets) September 30, 2017

Firstly, we should do our due diligence on any politico types that wanna come backstage. We didn't in this case, and that was lax. Sorry.

— al doyle (@aldoyletweets) September 30, 2017

Secondly, a tote bag round the neck is a crap protest; sorry. But that's all I had to hand, and I was very tired. Like, existentially tired.

— al doyle (@aldoyletweets) September 30, 2017

Thirdly, I don't have much right to wade into this debate as some Johnny come lately when it's not even my country, so sorry about that too.

— al doyle (@aldoyletweets) September 30, 2017

I just think that women's bodies are their own, and it's weird that anyone feels they can't just say that for any reason.

— al doyle (@aldoyletweets) September 30, 2017

Nancy totally fucken took him to task as well, it was uncomfortable and awesome.

— al doyle (@aldoyletweets) September 29, 2017