The pair - who recently split up - both attended the music festival and the 26-year-old model is believed to have given her former flame the cold shoulder during their ''awkward'' encounter.
A source said: ''It was a very awkward situation. Karrueche wouldn't even look at Chris at the party. She was dancing with her pal Christina Milian, only yards away from him, showing exactly what he was missing out on.
''Karrueche looked really great, and she knew she would push Chris' buttons by doing this. It was almost like she was dancing for him, but not even acknowledging he was there.''
The incident is said to have left the 'Yeah 3X' hitmaker fuming as he watched on from a nearby table.
The source added to HollywoodLife.com: ''Chris was at a table, while she was parading herself on the dance floor having a great time. Neither spoke with one another, but it was like there was an elephant in the room that couldn't be addressed.
''There was one cursory glance Chris gave, but you could tell he was mightily peeved that she didn't come to him to say hello.''
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