Los Angeles, California - Khloé Kardashian's ex, Tristan Thompson, may have finally moved on – and KoKo isn't happy about it!

According to OK! Magazine, the 40-year-old Good American owner is said to be "devastated" over the NBA star supposedly seeing someone else.

Last month, Tristan was spotted at Giorgio Baldi with a mystery lady who rocked a skin-tight black dress.

Those close to Khloé suggest that she's upset because the Cleveland Cavaliers player's new girl is "someone that everyone is saying looks like a knockoff version of her sister, or even her," which has "added knife in the heart."

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The insider explained, "It's bad enough that he's dating again. That's very hurtful because it's another clear reminder that he's not interested in her anymore."

The denim mogul, who shares two kids with Tristan, has said that she's over her troublesome baby daddy – according to her confessionals on The Kardashians, at least!

Yet, the sources maintain that Khloé's loved ones are urging the reality star to "not be jealous," but she's "taking it very badly." Will KoKo get some peace of mind amid her ongoing Tristan drama?