Like others have said, she's waving enough red fags to string bunting around. My daughter (28) is like this girl - she has various PDs, actual diagnosed medically ones, including NPD. When she was at the height of crisis, her delusions of grandeur became ridiculous, very obviously lies (she's sold scripts to Paramount, which have been big budget series/movies... but they've not credited her, for example) - she also went out of her way to destroy the lives/reputations of the two people who were trying everything to get her the help that she so clearly needed. Me, and her then-best friend.
Me, she lied to the police about having abused her, in an admitted effort to have me slung in prison (whilst innocent of what she was claiming that I'd done) and her younger brother put into the Care System (which he wouldn't have been, because he would have lived with his Dad). Fortunately, I could prove that she'd been plotting that for a year or more, otherwise... yeah. Life ruined, and my son's heavily disrupted. However, the police did push through for her to be psychologically examined (again, all my fault... she didn't need it, apparently, but the police know who's lying to them and who isn't when they have all the facts and irrefutable proof laid out in front of them).
Her best friend was also a calculated thing. Said friend was planning to go to Camp America for a year and work with deaf children (she's deaf, herself). My daughter persistently contacted the organisation stating that friend was mentally unstable, abusive, shouldn't be accepted on to the programme. When the organisation said that they'd interviewed friend and she'd passed every test with flying colours, my daughter did what a previous poster warned about... and doubled down. Camp America contacted her friend and said "WTAF is going on here?!", very understandably, and daughter only stopped when her now-ex-friend had to engage a solicitor to send several cease and desist letters to my daughter. Who was outraged that she'd lost a friend, furious that she still went to America for a year - and had had the guts to stand up and say that my daughter was slandering her.
The older daughter gets, the delusions continue (but are now health focused, and I recently went NC with her for my own health reasons, so... she is officially her boyfriend's problem). But this might be why she's "bigging herself up" to your son/you - because her own parents, who probably haven't done anything that she's insinuated that they have, are at their wits end and have had enough. In my situation - and, @thedudescocktail, this is my warning to you/your son - I and her then-best-friend knew the truth and/or that she was lying. My daughter tried to destroy us, mother and best friend, because we were a threat to the delusional reality that she was projecting about herself. Her last boyfriend literally ran away from the south-east to Aberdeenshire, to get away from her lies. She now tells anyone who asks that he was abusive. My money's on him just realising what was trying to manipulate him - and, quite naturally, wanting no part in it.
Just warn your son to be extremely careful. And to call the police for a welfare check every time she says that she's tried to harm/kill herself. She is not his responsibility - but if he stays with her, his life will never be quiet or peaceful.