She's right. LOL is a problem. It probably never meant that the writer was literally "laughing out loud," but now people just sprinkle it around for no good reason. Or just to make something really objectionable seem less so. Like "Yah well I used to kill rats with firecrackers lol." THAT'S NOT FUNNY. Or "I luv Justin Beiber lol." U R STUPID.
Realizing the problem years and years and years ago, but still needing some kind of way to signal that something's funny, we developed IFYCA and now you may use it too. IFYCA means "I Find Your Comment Amusing," and is the grownup version of LOL. Thusly:
The Sister: "I ate some chocolate cheesecake yesterday and now I am spiralling into a black hole of depression and self-loathing."
So feel free to adopt IFYCA and use it in your peer group too. You'll be happy you did! END THE TYRANNY OF LOL!!!