A source told The Sun newspaper: "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."
The 25-year-old pop megastar has already been warned off Taylor by pals after Brittany - an estate agent from San Diego - claimed she was still in a relationship with the actor when he first started dating Gaga.
A source previously said: "All of her friends are telling her to watch her step - Taylor is bound to break her heart. It's only a matter of time before he finds someone else."