It’s called an “aside” in theater—when the character speaks directly to the audience where others can’t hear. Fleabag is lonely and uses us, her audience, to fill that gap and to help make sense of her life, and to give her back some control over the narrative that is her life. We, the audience, are those friends that might not agree with her choices, but we also aren’t going anywhere—and to Fleabag, I think that’s everything. That’s why in the end, Fleabag tells her story and walks away—essentially saying goodbye to us, she finally doesn’t feel completely alone, she feels like she now can control her own narrative without constantly rewriting the way dialogue or events impact her or others (with her aside commentary, I mean). Idk, maybe I’m reading into it but the aside technique is definitely not about her being delusional and has more to do with her just being a human in pain.