The Bring It On star has been dating the Miami Heat ace for three years, and is a regular on the front row at his games.
But Wade felt forced to urge her to stay at home when he plays, because she shouts and screams while he's trying to concentrate.
She tells talk show host Conan O'Brien, "That (watching the games) got killed when I became too vocal. He was like, 'We're going to need you to sit a few rows back because I can hear you.'
"I'm like a dance mum: 'Plie! Plie... it's bad. I scream 'brick!' and 'air ball!'"
And Union admits she was left feeling guilty when the abuse she was hurling at her beau's rivals went too far: "There's a gentleman, who shall remain nameless, who was a little overweight, and I did yell out his name and 'Your Spanx are showing!' He looked at me - because I timed it perfectly for maximum effect - and he looked hurt. Then I felt like an awful bully."