The source said: "The stuff she has had to deal with has been tough to take.
"She is genuinely worried about her safety. There are concerns that the worst could happen if things get out of control."
Neighbours reportedly rushed to help Clarke, fearing she had been hurt in the attack on her Essex property. The yobs then fled the scene, leaving her in floods of tears.
A friend said: "It was horrific. Abi was understandably shaken by what happened.
"When neighbours went round to offer support she was having a panic attack.
"It had all come out of nowhere and she didn't know what to make of it. She was sobbing and shaking."
She has since been the victim of vile taunting in the streets and online. One source told The Star: "People have been shouting at her. She's also had nasty messages on Instagram."
Clarke did not call the police after previously being told her life in the public means nothing can be done, they added.
But she still hopes to publicly support her boyfriend when he clashes with UFC lightweight champ McGregor, 29, on August 26.