Struggling with My Sister's Dishonesty and Lack of Respect Towards Our Parents

Assalamu alaikum, everyone. My sister is 23 years old and, honestly, she has a serious problem with lying. She makes up stories about everything, from small things like whether she's eaten to big ones like failing a class at university. Recently, she got caught in some major lies-she claimed she had a 12-hour internship, but our parents discovered that on two days, she left early to go out with friends to the mall and movies without telling anyone, even turning off her location and dashcam. It's like she doesn't even see what's wrong with it! Our parents have lost all trust in her, and I could go on and on about how much she lies and disrespects them, but I'm here for advice, not just to vent. Also, while at the mall, she bought some clothes that aren't really appropriate according to our family's values. Our parents are pretty sharp-they started looking into things and caught her in a whole mess of lies, so she got into huge trouble a few days back. Now, they just had another argument because they found one of the items she bought and asked why she hid it from them. She just said, "I don't need to tell you everything I buy." So, what can my parents do, and what should I do as her sibling, when someone this old won't listen to anyone, even after being lectured? My mom is really worried she might take it even further. Just to be clear, my parents have no issue with her going out with friends or spending money-they just want honesty, that's all. If she wants to buy something, she should use the card. Don't use cash if there's nothing to hide, right? She used cash to cover her tracks, even though she doesn't have a job and all that money came from gifts from family over the years. She pulled off a big lie back in October that our parents caught, and now this happens again? It feels like a never-ending cycle that won't stop.