It was in Toronto where the unlikely partnership began to blossom following Grahm's move from his native Montreal.
"We've gone through some ups and downs," she says flashing her newly acquired leggings. "But we're here now - stronger than ever.
"We're completely different people - now we've learned to accept each other's differences.
"It's like a family now. He's the big brother I never really wanted but I got him and I'm the little sister he never wanted."
Thunderheist's coalition actually began as a technical mistake.
"I dragged this mix I'd done into my friend's Messenger window but it wasn't his Messenger window, it was Isis'," explains Grahm.
"I figured she would be like, 'He's a freak I'm not working with this guy, he's like Tiesto or something'.
"I didn't hear from her for two days and I was like, 'That's it, it's over'.
"Then she got back to me and she was like, 'Wow what was that?' She'd recorded over all the bits that were instrumental and I was like 'Yep this is gonna work'."
Ditching hip hop
Before Thunderheist was officially forged, the pair both enjoyed success with their own individual projects.
"I was considered the one who was going to save hip hop," Isis winks. "I've been writing and freestyling with men since I was about 13 so it was just natural for me."
Isis swings Grahm a knowing glance.
"In a long story short I saved Grahm's career," she giggles.
Grahm: "And vice versa!"
"He saved me from the lonely cold world of hip hop," she says. "Hey I guess in the end we do need each other.
"Without him I'd be a wreck and without me you'd not be any fun.
"It's [Thunderheist] our escape from boring yo yo yos and silly men in baggy jeans."
Key to Thunderheist's manifesto is the lack of one at all.
"It's a free zone - do whatever you want, be whoever you want to be," Isis explains of the group. "Because life is too short - you've just got to go for it.
"Our first show happened about three weeks after we'd started the band so we've been writing music that's fed off our live show."
I want to find the shyest girl in the crowd and make her lose her mind
And what a live show, Isis snaking between slack-jawed audience members whilst "Grahm ODs on bass" up on stage - it's an enthralling two-person spectacle.
"I want to find the shyest girl in the crowd," admits Isis. "And make her lose her mind."
And she's not coy about her last visit to the UK back in December.
"I'm going to send a very stern but fair letter to your government and request that you export at least 50% of the really good looking men to Canada!"
The first you're likely to hear from the group is the volcanic single Jerk It, taken from their self titled debut it set to be released in April in the UK.
"It's not about sex - it's about people completely losing it," says Isis.
Thunderheist: Grahm and Isis meeting Radio 1
"I wrote that song for every person who thinks they're too fat, too ugly, too geeky, too black, too white.
"It's about people owning what is them and embracing it and not apologising for themselves.
"I wanted to call it [the album] Thunder Thighs but no biggy," she swings a mischievous look at her partner in crime as Newsbeat departs. "It's not like I really have any creative control over anything…"
Another argument brews. A couple of hours later they'll start an impromptu midnight street rave in an East London Street with hundreds of passers by getting involved.
Typical of Thunderheist - with them, expect to sweat.
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