Even if she has never heard the irritating saga of Colin The Paper Boy, she probably has enough of a handle on Elly to realize that when she was the age she was when she got moved to Milboring, she was an awkward young girl throwing herself at someone who rightly saw her as a ludicrous and disruptive annoyance. This means that Mrs Patterson clearly seems to have believed "HUM! Since Colin just wasn't into me and I was too stubborn to admit it, it stands to reason that despite my not actually knowing what's going on in Molly's life, this boy must be the same sort of jerk!" She also figured out that Elly went on to think "I don't have to know what's going on because my past is clearly her present."
This means that Elly witlessly bought into to Connie and Greg's baffled squealing about how Molly was EMBRACING THE DARK SIDE OF LIFE because she too was an imbecile of a baby-boomer constitutionally unable to realize that the kid clearly blamed herself for her parents' marriage going kablooie. Since Jim's generation celebrated their victory over Hitler by giving birth to a generation of knuckle-dragging cretins like Connie, John and Elly, a child who's simply acting up because she doesn't know what really happened got screamed at because her step-mother and her pal are simply too dumb to understand what's going on around them. She also has no idea why Molly hasn't heard from this kid. Maybe someone's intercepting the mail. Maybe his parents think Molly is a hussy because boomers are muttonheads and goose-steppers. Maybe he has no idea what her address actually is. Elly doesn't know and doesn't care because some older boy who already HAD a girlfriend laughed at the child too dim to notice that.