The 25-year-old singer ordered Brittany Sackett to leave beau Taylor Kinney's alone after she kept interrupting their Vegas romantic meal for two with angry phone calls, according to The Sun.
A source told The Sun, 'Brittany is extremely jealous.
'But as crazy as Gaga is, she's also a very good person and has a real sense of womanhood, and looking out for other women.
'She and Taylor only started dating a few weeks ago, despite feeling sparks when they met on the set of her You And I video almost three months ago because it was the right thing to do.
'But she wants to be left alone to enjoy her new relationship now.'