The singer and actress, who is 30 years old, spoke out on Instagram Stories on Friday after Bieber, who is 26, told her about the online hate she is getting.
Gomez wrote, "Hailey Bieber reached out to me and told me that she has been getting death threats and other hateful things."
"This is not what I believe in. Hate and bullying should never happen to anyone, "she told me. "I've always been for being kind, and I really want all of this to stop."
Fans of Gomez have recently fought with fans of Bieber, a model who is married to Gomez's ex-boyfriend Justin Bieber, and Jenner, a TV star and beauty mogul.
In February, Gomez posted a clip on Instagram Stories in which she said she "accidentally laminated" her eyebrows too much.
Jenner posted a selfie with the words "This was an accident?" written over her brows the same day.
Jenner also posted a screenshot of herself and Bieber that showed their eyebrows up close.
Many people on social media thought Jenner's posts were making fun of Gomez, which Jenner denied on TikTok on February 22.
"This is going too far. Selena has never done anything wrong, and I didn't see her eyebrow posts. You guys are making something out of nothing. This is nonsense, "Jenner wrote.
"Agreed @kyliejenner All of it is pointless. I really like Kylie!" Gomez responded.