What’s the point in lying ?

What’s the point in making a web of lies and constantly doing it ? I have a sister that does nothing but lie . Like she diagnoses her and her man with different medical conditions, but neither one goes to the doctor . She claims she has pcos because she’s over weight , but yet has never been formally diagnosed , she claimed she had a MC ( got a d&c ) but supposedly the hospital that did the “d&c” did it while she was awake , didn’t give her anything for pain and let her go home 30 minutes later , the same exact hospital not 2 months before I had a MC & they had to transfer me to a different Hospital because the hospital doesn’t specialize in baby stuff and hasn’t for YEARS . Also now she’s claiming she’s had 3 MC’s ( the same as me ) also I have pcos , like she claims to have . She says that she’s losing weight , but then two hours later says that she never said that , but posted it on fb . She used to steal my other sisters pregnancy test ( positive ones ) and claim they were hers and had everyone believing she was pregnant as well . She celebrates mother’s day , but has never been pregnant at all . Her man is Infertile and she swear up and down he isn’t . ( I only know that because he has had his sperm tested ) she doesn’t know he has . Like I just don’t understand why lie about such little and also tragic stuff , it makes NO SENSE at all . If you confront her she acts as if , I’m the pathological liar , but I have proof to back up everything and she knows that , but says that I’m lying on her . She’s not the only one like this , my other sister does this to and I don’t understand why , like one day she took a shower at my house and used all the hot water and claimed that she never took a shower ? Like it’s little things and big things they both lie and I don’t get it ? I’m the youngest of the sisters and have a little brother . But my little brother and I don’t do none of the above . Like of course everyone tells white lies ( to save from going to events , or getting extra sleep and etc ) . But my sisters go all out with the lies . Like both sisters have claimed to be raped but then years later admit it never happened and that they never said that it did , but there was police reports filed and everything . Someone please give me some insight , because I can’t handle it anymore .

No I’m not oblivious , I know it sounds like they have mental disorders . I know like it sounds like something deeper within , but I don’t feel sorry for neither of them . Because when someone lies about a MC they’ve never had , I don’t take that lightly & the other sister is a drug of all kinds type of person . But the other sister that suffers from infertility , she chooses not to go to a OBGYN , she chooses not to look into getting help or find out out what’s going on . I know for 100% fact infertility is hard to deal with , but she claims she has Endometriosis , pcos , polyps , cyst and everything that I have in general & everytime I MC , she does to supposedly .

The other sister is just as toxic , doesn’t take care of her children , let’s everyone else take care of them because she just can’t do it . I posted in this group because I was told I couldn’t post it anonymously . But I posted this topic anonymously because idk if either sister uses Glow . I’ve tried suggesting counseling, but neither of them think nothing is wrong . The other sister got a man thrown in jail , saying he raped her but never did . & she admitted that while drunk . He just pissed her off and so she cried rape . They let their child hold friend molest me for years and always said I was a liar and it started happening when I was 6 until I was 9 . I just can’t deal with their constant crap everyday .