The 38-year-old blasted the bullies after Emily, 16, received taunts following her audition for The Voice.
Emily performed in front of judges Will.i.am, Ricky Wilson, Tom Jones and Rita Ora but none of them turned around during the blind audition.
As a distraught Emily was seen being comforted by Kym, the Coronation Street star sent a furious tweet to the trolls.
She wrote: "Got to say the bullies on here make me sick!! Say what you like about me I really do not care but a 16yr old??? Really?? Sick!!! [sic["
Kym's Corrie co-star Catherine Tyldesley also leapt to Emily's defence, replying: "@msm4rsh pure jealous. Pity them- for they live in world of deep will never forfil their dreams. #karmawillprevail x [sic]."
Earlier in the evening Kym tweeted praise for her daughter and promised it would not be the last people saw of her.
She said: "I am solo proud of my daughter at 16 she is just a baby and she was so nervous but this is not the end for her this is just the beginning [sic]."
Kym found fame in 2000 when she won reality show Popstars with band Hear'Say. She left the group in 2002 and went on to release a solo album before moving on to acting in Coronation Street.