So here's her agent explaining:
"Parker attended all USA Basketball training camps leading up to the 2016 Olympic team selection, but was inexplicably omitted from the final roster, despite being featured in a promotional ad. Lelchitski said Parker’s decision not to attend camp this fall was because of that experience. “Hell yeah she turned it down,” Lelchitski said."
So it's because of her anger and bitterness at being left off the Olympic team. That's understandable. So she isn't just refusing to show up. She's seriously pissed off at being left out of the Olympics, a decision that USA Basketball refuses to explain.
USA Basketball is the one looking bad here. Hands down.