Question: Which musician co-founded Throwing Muses with her stepsister Kristin Hersh: Tanya Donelly or Kai Hansen?

Context paragraphs:
Throwing Muses: Throwing Muses is an alternative rock band formed in 1981 in Newport, Rhode Island, that toured and recorded extensively until 1997, when its members began concentrating more on other projects.  The group was originally fronted by two lead singers, Kristin Hersh, and Tanya Donelly, who both wrote the group's songs.  Throwing Muses are known for performing music with shifting tempos, creative chord progressions, unorthodox song structures, and surreal lyrics.  The group was set apart from other contemporary acts by Hersh's stark, candid writing style; Donelly's pop stylings and vocal harmonies; and David Narcizo's unusual drumming techniques eschewing use of cymbals.  Hersh's hallucinatory, febrile songs occasionally touched on the subject of mental illness, more often drawing portraits of characters from daily life or addressing relationships.

Throwing Muses (2003 album): Throwing Muses is an album by the alternative rock band Throwing Muses.  It was recorded over three weekends and released simultaneously with Kristin Hersh's solo record "The Grotto" on 17 March 2003.  The album features Bernard Georges on bass and David Narcizo on drums as well as original bandmate Tanya Donelly on backing vocals.

The Breeders discography: The discography of American alternative rock band The Breeders consists of four studio albums, one live album, three extended plays, ten singles and twelve music videos. Kim Deal, then-bassist of American alternative rock band the Pixies, formed The Breeders as a side-project with Tanya Donelly, guitarist of American alternative rock band Throwing Muses.  After recording a demo tape, The Breeders signed to the English independent record label 4AD in 1989.  Their debut studio album "Pod" was released in May 1990, but was not commercially successful.  After the revival of the Pixies and Throwing Muses in 1990, The Breeders became mostly inactive until the Pixies' breakup in 1993.  With a new lineup, The Breeders released their "Safari" EP in 1992, followed by their second studio album "Last Splash" in 1993.  "Last Splash" was The Breeders' most successful album; it peaked at number 33 on the United States "Billboard" 200 and was certified platinum by the Recording Industry Association of America in 1994.  The album spawned the band's most successful single, "Cannonball".  The single peaked at number 44 on the US "Billboard" Hot 100 and at number two on the "Billboard" Alternative Songs chart.

Limbo (album): Limbo is a 1996 album by the American alternative rock band Throwing Muses, released on Rykodisc.  The album was recorded at the same New Orleans studio the band recorded "University".  Following a tour for the album, Throwing Muses were dissolved, with Kristin Hersh continuing her solo career and David Narcizo and Bernard Georges working on several personal and music projects including Hersh's.  The album, engineered by Trina Shoemaker, also features cellist Martin McCarrick and Robert Rust on piano.

Tanya Donelly: Tanya Donelly (born July 14, 1966, in Newport, Rhode Island) is an American Grammy Award-nominated singer-songwriter and guitarist based in New England who co-founded Throwing Muses with her stepsister Kristin Hersh.  She then went on to work in The Breeders and Belly in the 1990s.  In the late 1990s, she settled into a solo recording career, working largely with musicians connected to the Boston music scene.

The Blizzard of 78: The Blizzard of 78 is an American rock band from Boston and Providence.  Consisting of ex-Delta Clutch members, they currently have two albums released; the first being the critically acclaimed "Where All Life Hangs".  Tanya Donelly contributed a guest vocal to the album, and it won several Motif Magazine awards in 2007.  The Blizzard of 78 have played with, or opened for, Coldplay, Alex Chilton, Ronnie Spector, Snow Patrol, Jim Carroll, Tanya Donelly, Guster, Remy Zero and Throwing Muses.  The group once performed The Replacements' album "Tim" in its entirety.

Red Heaven: Red Heaven is a 1992 album by the American alternative rock band Throwing Muses, released on Sire/Warner Bros.  Records.  Recorded at The Power Station and Fort Apache Studios following the departure of Tanya Donelly and Fred Abong, "Red Heaven" was recorded by Kristin Hersh and drummer David Narcizo with help from former bassist Leslie Langston.  Former Hüsker Dü vocalist/guitarist Bob Mould took time off from his new band Sugar to record vocals for "Dio".  Initial copies of the album came with the otherwise unavailable Kristin Hersh solo acoustic album "Live at Maxwell's Hoboken".

Kai Hansen: Kai Michael Hansen (born 17 January 1963) is a heavy metal guitarist and vocalist.

The Grotto (album): The Grotto is the sixth solo album released by Kristin Hersh.  It was released on 17 March 2003 on 4AD records, simultaneously with the Throwing Muses (2003) record.  It features Howe Gelb on piano and Andrew Bird on violin.  Kristin Hersh produced the album as well as playing all other instruments.  The album peaked at #39 on the US's Billboard Top Independent Albums Chart.

Hips and Makers: Hips and Makers is the debut solo album by Kristin Hersh, best known as the primary singer and songwriter of the band Throwing Muses.  The album was released by 4AD in the UK on January 24, 1994, and by Sire Records in the US on February 1, 1994.  In contrast to Hersh's rock-oriented work with Throwing Muses, the album is primarily acoustic, with Hersh usually playing unaccompanied.  Other credited musicians include Jane Scarpantoni on cello and Michael Stipe of R.E.M., who sings backing vocals on the opening track, "Your Ghost."  In addition to Hersh's own material, the album features a cover of the traditional song "The Cuckoo".

Supporting paragraphs: Tanya Donelly Kai Hansen
Answer: Tanya Donelly