Cissy Houston's Family 'Devastated' by Her Death: 'She Lived a Long, Blessed Life' (Exclusive Source)

Cissy Houston's family is "devastated" by her death, a source tells PEOPLE.

Cissy, mother of the late Whitney Houston and a legendary gospel singer herself, died at 91 on Monday, Oct. 7 at her home in New Jersey. She was under hospice care for Alzheimer's disease.

"The family is taking it hard," says the insider. "They’re getting through, but it is very difficult right now."

The source added that Cissy (born Emily Drinkard) "lived a long, blessed life."

On Monday, Oct. 7, Cissy's daughter-in-law Pat Houston confirmed the news of her death in a statement.

“Our hearts are filled with pain and sadness. We [lost] the matriarch of our family,” she said. “Mother Cissy has been a strong and towering figure in our lives. A woman of deep faith and conviction, who cared greatly about family, ministry, and community. Her more than seven-decade career in music and entertainment will remain at the forefront of our hearts."

Pat added: "Her contributions to popular music and culture are unparalleled. We are blessed and grateful that God allowed her to spend so many years with us and we are thankful for all the many valuable life lessons that she taught us. May she rest in peace, alongside her daughter, Whitney and granddaughter Bobbi Kristina and other cherished family members."

Cissy was also an aunt of singers Dionne Warwick and Dee Dee Warwick.

Cissy began her singing career in 1938, joining her sister Anne and two brothers Larry and Nicky in a group called the Drinkard Four.

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Cissy formed a group called the Sweet Inspirations in 1963 with Dee Dee. A few years later, the band was providing back-up vocals for artists like Otis Redding, Dusty Springfield and Wilson Pickett. They ended up working with The Jimi Hendrix Experience in 1967 and Elvis Presley in 1969.

In 1963, Cissy released her first solo track, "This Is My Vow"; however, in her earlier records her name was spelled "Sissie" Houston. In 1970, she released her solo debut LP Presenting Cissy Houston, which included hits such as "Be My Baby" and "I'll Be There." Two years later, she sang backup on Bette Midler's debut LP.

During her life, Cissy won two Grammy awards — the first in 1996 for best traditional soul gospel album for Face to Face, and the second in 1998 for her album He Leadeth Me.