It would be somewhat unfair to deem Lady Wishfort "repulsive" because she does change towards the end of the play. She shows some positive qualities and she also proves to have her maternal instincts in check by protecting her daughter from being duped.
Yet, to agree with your argument, Lady Wishfort does reunite a number of qualities that might seem shocking to her peers, and maybe repulsive to men.
First, she literally blobs herself with face paint (make-up) to hide her signs of aging. Second, she acts as if she were a love-crazed teenager when, in fact, she is a woman in her 50's (quite old for the time this play was produced -1700's) and openly displays the behaviors of a man-eater.
Hence, the image of a big, older lady, ladden with makeup, and making advances at younger men, could indeed prove repulsive to those who are the victims of the advances. Lady Wishfort's inability to recognize herself as an aging, hefty lady and her wild, sexual desire for men definitely play a part in finding her character somewhat repulsive.