Why is she starting the sentence with the past progressive tense?
Native speaker’s answer
Rebecca
The past progressive tense is used in the beginning of the sentence here because it is part of a story she is telling. When retelling a story, it is common to use the past progressive tense to either give background to the story, or to describe an action that is still in progress in the story as it is being told. So in this case, she uses past progressive tense for "we were hanging out last night" to express that this action was still continuing when the other action occurred, or when she asked her to do her eyebrows.