In late November, the reality starlet and Canadian model Gabriel Aubry caught a Lakers game and stepped out to watch the movie Burlesque. They then quietly went their separate ways, and by early December, Kardashian was dating pro basketball player Kris Humphries.
But sources say that one person took the brief episode seriously: Aubry's ex, Halle Berry.
"Halle was very upset," says a source close to the actress. "She was upset at the idea of someone like that being in her daughter's life. She did not want a reality star in Nahla's life. She was very aggravated."
Another source close to Berry, 44, says the Oscar winner's reaction had nothing to do with jealousy.
"Halle couldn't care less who Gabriel dates," says this source. "She just didn't want Nahla exposed to the cameras that are undoubtedly around a reality star."
A source close to Gabriel says Nahla was never near Kardashian.
"Gabriel wanted to make sure he dated someone for six months before he introduced them to his daughter," says the source. "There was never for a second a thought by Kim or Gabriel that Nahla would ever go near cameras."
Either way, the brief time that Gabriel, 35, and Kardashian, 30, spent together has surfaced as one of several issues in the ugly custody fight over daughter Nahla, who turns 3 next month.
In November of last year, Berry and Aubry, who had been split for seven months, were raising Nahla in an informal joint custody arrangement, the result of what most outsiders had thought was an amicable breakup.
But then Aubry filed court papers to establish paternity and secure joint legal and physical custody of Nahla on Dec. 30, not long after Berry reacted to seeing him with Kardashian.
For much more on Halle and Gabriel's custody battle, pick up this week's issue of PEOPLE, on newsstands Friday
Reporting by JENNIFER GARCIA, ELIZABETH LEONARD and JULIE JORDAN