Bush said Gaga does not mind Taylor Kinney, who she has been dating for three years, getting close to her in the film, reported Contactmusic.
"(Gaga is) an artist through and through. There's no part of her that doesn't understand our job or thinks it's weird. I thinks she's probably the least threatened woman on the planet," Bush said.
The 32-year-old actress, who is in a relationship with Google programme manager Dan Fredinburg, also said that her first encounter with the 28-year-old singer was a little strange.
"It's always a little strange to meet the love of someone's life after you've swapped spit with their partner! But she's just the loveliest human being and so warm and welcoming - I've been such a huge fan of her for so long," she added.