Remember, Elly seems to see herself and her wants and needs as being the only ones that exist and it's sort of beyond her capabilities to quite understand what Thelma saw when she looked at the dentist's young wife. While Horsebun Elly is still trying to figure out why it was that being a mentor figure to Gayle Thomas didn't work out, she doesn't realize that Thelma saw Low-Hanging Ponytail Elly as being a similar sort of person in that what she saw was an angry, lonely mess without actual friends to help her raise her kids.
This is because Thelma would have had to see what most people saw when they looked at Connie and Annie. On the one hand, Elly made a love object of a clingy, needy, mousy neurotic living a life of noisy desperation barging over for a shoulder to cry on and with Annie, you have the too-clever-by-half type confidently spouting nonsense while denying her husband's obvious bad traits. Worse, the poor child is clearly too hung up on trying to please the same sort of blind-eyed house-proud shrew Thelma knew all too well growing up in Yorkshire; it was thus obvious that this poor angry young thing needed a good influence to keep her from doing perfectly nice children lasting damage. Since Elly doesn't know how damaged she is owing to her need to award herself positive traits she doesn't have, she doesn't understand that she was the target of a mentor. What she does know is that she already had a mother...which is kind of the problem.