Ashamed over her scandalous affair, “Twilight” star KRISTEN STEWART has virtually stopped eating and is basically “living on” a dangerous diet of Red Bull and cigarettes, say sources.

Friends are horrified at the guilt-ridden ac­tress’ gaunt appearance and fear for her health as she apparently punishes herself for betraying the love of her life, Robert Pattinson, 24.

The raven-tressed beauty, 22, made worldwide headlines when steamy photos emerged of her in romantic clinches with her married “Snow White & the Huntsman” director Rupert Sand­ers.

“Kristen is a nervous wreck and existing on a diet of cigarettes, sugar-free Red Bull and the occasional bag of potato chips,” revealed an insider.

“Whenever anyone tries to push her to eat even a small bowl of soup, she either claims that she’s just had something, which isn’t true, or that she’s nauseous and there’s no chance of keeping anything down.”

Kristen’s loved ones – especially her Holly­wood script supervisor mom Jules – are deeply concerned about her mental state and physical well-being, added the insider.

“They’ve been doing everything they can to lift her out of her black hole, but all she talks about is how ev­eryone hates her,” the insider confided.

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