Kara has forgiven and then fought besides criminals who have tried to kill her and her friends. Oliver having cheated (no matter who with) shouldn't get anymore than an 'ick' moment, esp as it is something from before she even knew him.
She respects the man he is now.
yeah that's not the issue . it's about his bad habits of always wanting to keep that stuff secret which he got from his parents and psyho waller. and the fact that when it came out in the worst way possible the person that it most damaged he didn't bother to say sorry about it still.
he just left it there. it's not about kara forgiving. it's about the person who he was supposed to have done so to which was Laruel and that former best friend of who he knocked up and had mommy take care of so he can continue to keep having sex with laurel, her sister & others.
current day he may not be sleeping around . but he didn't truly learn his lesson about keeping secrets and not speaking which made to iris say something about that via the current person he's with. and telling about important thing's they need to be aware of that moment or that time.
as for kara & what I said this goes back to both her women empowerment and respect for women that goes back to max lord who both Alex and kara stated is or was bad Oliver pre the island as much as he was a villain and she showed great distaste for that, about lord even though we barely saw Lord doing what oliver did all through his 20's . which pre her knowing him as well. but it was thing to her back then.
and mon-el with miss Tessmacker in the work place, as they put it he was frat boy and we saw how mad that made Kara . and they weren't even dating.
point is most of his (Oliver's) action's weren't always respectful to women ,if at all and part of his ego was at play there.
and we've seen that kara had some standard that conflict with herself . So she's not as forgiving as we like to put it. Lena found out the hard way. and there that weirdness some of her human friend from earth 1 being allowed to fight powered villain's and their poor argument when it come's to her friend from her earth which fall's apart especially when the writer's make sure absolutely to have the same thought/ view ,say the same thing's and stubbornness as her.
hell they brought back the issue of her not liking killing which both J'on & her aren't happy with Manchester black over. But Oliver does it very often of like the cross over befor this earth X. like it's second nature.
Though I think that more about the writers making to shifty on where she truly stands there.
I'm just saying there thing they like put up on her show often they make an over blown deal out of which both her and oliver should be in conflict about when you think about it properly. cause the writer like make the character of oliver go back to not learning his less with secrets ETc and how she views things. which become's double standared when it goes back to just being on her earth . which makes it off.