Most Helpful Girl
She has a problem. Most people lie for about 3 reasons 1. denial 2. To stall and 3. attentuon/exageration.
To me it could be a attention thing. Reason said is she will go as far to dramatizing something serious like rape. This usually makes people feel bad and comfort someone. And she may like that attention whether she needs that much attention or she didn't get enough as a child I don't know.
She may be a compulsive liar as well.
In that case maybe it's best you ask her to
get help whether it's counseling or something.
Or do what most people do and show her that her lies come with a consequence. if you know she's lying it doesn't matter if her mom your friends or stranger is in front of you guys. Call her out on it.