Eight days before the 61st Grammy awards, the woman with the most nominations is on a beach in Mexico having a massage.

Brandi Carlile is here in Cancún with her wife and kids – Evangeline, four, and Elijah, one – to organise and perform at the inaugural year of her all-female festival, Girls Just Wanna. But right now she is having a break from it all and reflecting on the fact that her sixth album, By The Way, I Forgive You, has gleaned six nominations, including in the three biggest categories of song, album and record of the year. Last year, the Grammys’ dearth of female winners came under scrutiny, and former president Neil Portnow declared that it was the women who needed to “step up”. The success of the pragmatic and political Carlile feels like the perfect rebuff.

At 37, deep into a 15-year career as a singer-songwriter of pop-rock, blues and folk, Carlile has a serene perspective on the Grammys. “I know I wouldn’t have been ready for this in my early 30s. I would have got stressed out, not slept, got sick, drunk too much. I would have gone wrong, you know? I know what it feels like to not have recognition. It doesn’t feel bad. But this feels a lot better.”

I realised I was waking up every day political, as a gay mother with two daughters

Carlile has never couched herself as staunchly country, yet this is her widest crossover to date. She had spent years writing introspectively as a lesbian with a nuanced outlook on love and struggle, a gay woman who was illegally married in 2012 before the abolition of the Defense of Marriage Act in 2015. Following Trump’s election, she understood that this was a revolutionary act. “I realised I was waking up every day political, as a gay mother with two daughters,” she says. “Being political doesn’t come from outside me any more. It comes from who I am.”

Her empowerment anthem The Joke is up for song of the year. It is for effeminate boys born into an era of hyper-masculinity, and for little girls unable to see themselves represented on the biggest stages. But for Carlile its meaning is ever-changing. The second verse was written about Syria (“They come to kick dirt in your face, to call you weak and then displace you after carrying your baby on your back across the desert”), and yet, less than a year later, she says: “It’s about our own southern border. When I sing it, that’s what I’m thinking of.”

‘How can we do the numbers when we’re not getting signed, we’re not getting on the radio?’ Brandi Carlile’s Girls Just Wanna weekend in Cancun last month. Photograph: Brian Stowell

Carlile was born “very poor” in a little town outside Seattle to parents who married young. After moving house every year, her dad was laid off and relocated the family to a white trailer “up half a mile of dirt road”. Her mother’s father died of motor neurone disease, and her mother, aged 30, and with a newfound carpe diem vigour, bought a PA system to start a band with the money he had left. If Carlile and her two siblings did their chores, they could sing at band rehearsals. “I was addicted,” says Carlile of music. “I’d write down lyrics and obsess about the people that sang them.”

She studied Tanya Tucker and Patsy Cline and started performing onstage by the age of eight. “Most of the time I ran around the woods. The rest of the time I practised country music and flunked out of school. Even elementary.”

Her entire family dropped out of high school. As school punishment for troublemaking, Carlile and her brother washed buses. One day the church got hold of them and Carlile began studying with a pastor. Around the same time, she decided to come out – Ellen DeGeneres had just done so and the 14-year-old Carlile followed suit. “I was out of the closet in school. Totally content to be out,” she says. The pastor wasn’t as relaxed, and refused to baptise her. “I had my swimsuit on under my clothes, they’d invited my family and friends – everyone,” she recalls. “That’s when they decided to make an example of me. I’d been on a lot of stages in my life, but that was an irreversibly damaging public humiliation.”

When writing her album, she realised it was a moment she hadn’t processed, hence the title: By The Way, I Forgive You. Carlile reckons the US could use some forgiveness. “We have to move beyond our resentment so that we can be productive.”

Her songwriting is brazenly honest: take the single, Party of One, which documents Carlile’s marital woes after her firstborn’s birth. Evangeline is biologically related to Carlile but was carried by her wife. “It was a strange setting-in of conflicting instincts: the birth mother having to win, me having to understand that I’m also a mother and not a father, but there not being a template. I was wondering if I was worthy of motherhood, whether maybe we aren’t supposed to do these things.” Not only did she confront her own “internalised homophobia” in songwriting, she wrote from a “super queer perspective” and wound up with something universally resonating. Straight couples tell her how much that song means to them.

She now has a collaborator in Sam Smith, a longstanding fan in Barack Obama, and a confidant in Elton John. With increased notoriety, she appreciates it might be harder to be outspoken, particularly in the country markets, but she sees no choice. I mention a recent interview I conducted for this paper with the singer Miranda Lambert – a “dear friend” of Carlile’s and a National Rifle Association supporter – who dodged political questions. “It’s irresponsible for country music not to address sensible gun reform,” says Carlile, having just written a yet-to-be-released song titled Cowgirls with the lyric: “The NRA can kiss my country ass.” “Because they can!” she says. “I’m not afraid to say that. I’m not afraid of who it alienates.

“[After the election] it was like somebody turned on the black light and we were surrounded by the filth of our own ideology and our own complacency,” Carlile says. “That’s when I realised I was part of the problem. To not squander the opportunity I’ve been given is an evolution. If somebody believes I’m wrong, I want them to say it so we can engage. Big inclusive sentiments are a salve. They’re not appropriate.”

The idea for the Cancún festival she has organised stemmed from a wakeup call she had five years ago. “I never saw progress going backwards,” says Carlile, who grew up attending Lilith Fair – the groundbreaking women-centric 90s festival. Carlile played a winter cruise ship – Cayamo – and a group of attendees complained about the number of women and gay people. “They called it Gayamo,” she cackles. “Gotta hand it to them, that’s pretty funny, but it was the first time I realised that people categorise entertainment according to gender and sexual orientation. Man, that ain’t cool.”

Carlile decided to make a virtue of the exclusion of women from festival lineups. “There’s an Instagram called bookmorewomen,” she says. “Have you seen it?” The account copies festival posters, but deletes all male names to highlight what’s left. Some are 100% blank. “I spend a lot of time arguing with promoters in the comments,” she says. Bookers claim that there aren’t enough women artists to book. “The argument is that women have to be viable in the market, but how can we do the numbers when we’re not getting signed, we’re not getting on the radio? This merit-based ideology is so flawed. It’s gotta start somewhere. Could it be with you?”

Brandi Carlile (right) and Mavis Staples (left) at Girls Just Wanna. Photograph: Brian Stowell

She’s grateful that she came of age amid the pastoral care of Lilith Fair, where she was told to reapply sunscreen by strangers and to go and get some sleep. Recent US studies have shown up to 90% of female concertgoers experience sexual harassment at gigs and festivals. “That’s not because of men, it’s because of toxic masculinity,” says Carlile. “If there were more women onstage, there’d be more women in the audience.” She realises her daughters are going to want to go to the likes of Coachella and Bonaroo when they come of age. “You know how terrifying it is to raise daughters knowing that?” she asks. Would she let them go? “On principle I’d ask to see the poster. If it wasn’t 50% [equal representation] I’d say no, for any festival, which would mean probably almost all of them now.”The Grammys stage on Sunday, at least, will set a thrilling example for her kids. She has already revealed that she plans to perform The Joke at the ceremony: a chance to subvert a typically politically light event. “It’s a call to action,” she says of the song. “It’s me saying: we still have a chance to turn it around. I don’t have a Messiah complex, but I do want people to hear that message.”

Does she want to win? “Oh my God!” she says, as though the thought actually hasn’t crossed her mind. “I don’t know if it’s about wanting to win. I fucking care so much about the nominations. I’m never going to be one of those people who plays it off. I wanna wear the right clothes, I wanna have a great time, I wanna drink champagne. I don’t know if I’m gonna win. I don’t know if I wanna win. But I know that I don’t wanna let anyone down.” Her smile starts to look a little pained, a smidgen sad. “I just don’t wanna feel embarrassed,” she says. “I hate feeling embarrassed.”

• This article was updated on 8 February to correct an error – it was Carlile’s grandfather who died of Lou Gehrig’s disease, not her father.