The 26-year-old singer is in touch with some people from her formative years, and gets nervous when she has to hang out with the popular crew, reported Contactmusic.
"I am throwing my best friend an engagement party this weekend, and I'm going to be seeing all these girls from school, and I would be totally lying to you if didn't say I was worried about how I'm going to look," Gaga said.
"I was saying earlier, 'I have to look fabulous, I have to look absolutely amazing, some of them were horrible to me'," she added.
However, she is unsure why women are often nasty to each other, and thinks more effort should be made to be nice.
"I think people are just, for no reason, wretched to each other all the time, and I don't think they use clothes or men or perfume or make-up or anything more than they use anything else. We should all make an effort to be nice to one another all the time," she said.