What part of any of that translates into abuse, rape and being abandoned by everyone she ever loved?
As far as rape goes, fucking nothing. Lily has fabricated an allegory that "Arthas Raped Sylvanas" because it validates her own feelings towards her and allows her to project herself onto Sylvanas much easier. Whether or not Lily was actually raped in the past, she fully believes she was, and because she has so fully invested herself in Sylvanas (an investment that started purely out of spite in the beginning because she didn't like the story Blizzard was telling) she has started to ascribe her own traits onto Sylvanas.
Lily only came to her realization that she was "raped" months after the supposed event happened. Likewise, she only started blowing this "Arthas Raped Sylvanas" horn lately because she has convinced herself it is true, and if you don't believe it you deserve to have your head bashed in because you're obviously a misogynistic fuck.
As far as abuse, yeah, Arthas did torture her and force her to murder her own people, that would fuck anyone up.
For abandonment Lily loves to harp on about how Quel'thalas' former allies (The Alliance) only saw The Scourge whenever they looked at any Forsaken and actively hunted them. Which, I mean yeah, being so blind was a bad move on the Alliance's part.
But she also loves to bitch and moan about her living sisters, Vereesa and Alleria, """abandoned""" her. She will never address the fact that Sylvanas planned to murder not only Vereesa but also her children to raise them into undeath. And THEN she planned to murder both of her sisters and raise them into undeath AGAIN.
Like, letting them live was never an option in Sylvanas' mind, and Lily is perfectly okay with that because Sylvanas can do no wrong.
To Lily, Warcraft is very black and white with no room for any subtlety. The Alliance are all religious Nazis, The Horde are all blithering idiots obsessed with honor, and Sylvanas is a paragon of everything she perceives as right. What started out as her liking a character from Warcraft 3 and having her obsession with said character grow purely out of spite for the direction the story took has spiraled into an absolute shitstorm that is purely indicative of Lily and her fanbase.
It's also super fucking ironic how much Lily lambasts the shit out of the Diamonds in Steven Universe for being fascist, genocidal monsters... And yet her absolute favorite character ever is a fascist, genocidal monster that has abducted, tortured, and attempted to brainwash her own people. Oh, but it's totally fine to genocide the Night Elves... because Sylvanas did it... And that makes it perfectly okay and the right thing to do.
As someone who has been big into WoW since it first launched it's absolutely infuriating to watch it be completely misread, misrepresented, and bastardized in atrocious, self-insert fanfiction. It's even worse when the person that is doing the horrible bastardization continues to just plug her ears and yell at the top of her lungs over anyone trying to even just understand her side or clarify points she misread.
TL;DR: Lily continues to consistently misread and ascribe attributes onto Warcraft characters that don't fucking exist because it validates her own feelings on the characters.