Love inherited 98 percent of the group's publishing rights when her husband, Kurt Cobain, killed himself in 1994. The other 2 percent was split between former Cobain bandmates, Krist Novoselic and Dave Grohl, Rolling Stone said.
Love told the magazine she sold a quarter of her share to former Virgin Records General Manager Larry Mestel, now of Primary Wave Music Publishing.
Love said she took Mestel on as "a strategic partner" because managing the estate herself was "overwhelming."
"The affairs of Nirvana are so massive and so huge, and they've all fallen on my lap. I own almost all of (the publishing) ... and it proved to be too much for me," she told Rolling Stone.
"I needed a partner to take Kurt Cobain's songs and bring them into the future and into the next generation. And this guy's the guy to do it."
Sources said Mestel probably paid more than $50 million for the rights.