Did Williams make a slip in having Amanda say Laura is a "crippled"?

Amanda does her best, throughout the play, to avoid referring to her daughter, Laura, as a cripple. As stated by Laura, herself, she had "an attack of pleurosis" in high school which left her with a weakened leg that necessitated the wearing of a brace. In the play, Laura walks with a visible, though slight, limp.

Twice during the play, the idea that Laura is a cripple arises and is quickly denied by her mother:

1)

AMANDA: Girls that aren't cut out for business careers usually wind up married to some nice man. [Gets up with aspark of revival.] Sister, that's what you'll do !

[LAURA utters a startled, doubtful laugh. She reaches quickly for a piece of glass.]

LAURA: But, Mother

AMANDA: Yes ? [Crossing to photograph.]

LAURA [in a tone of frightened apology]: I'm - crippled !

AMANDA: Nonsense ! Laura, I've told you never, never to use that word. Why, you're not crippled, you just have a little defect - hardly noticeable, even! When people have some slight disadvantage like that, they cultivate other things to make up for it - develop charm - and vivacity and - charm! That's all you have to do ![She turns again to the photograph.] One thing your father had plenty of - was charm!

2)

TOM: Mother, you mustn't expect too much of Laura.

AMANDA: What do you mean?

TOM: Laura seems all those things to you and me because she's ours and we love her. We don't even notice she's crippled any more.

AMANDA: Don't say crippled ! You know that I never allow that word to be used !

The last time the word is uttered, Amanda finally admits what she really thinks of her daughter's condition. It is said in a fit of anger and disappointement. It was not a slip of Amanda's or of the playwright. Amanda finally has to face one of the many bitter truths of her sad and all but hopeless life:

TOM: I'm going to the movies.

AMANDA: That's right, now that you've had us make such fools of ourselves. The effort, the preparations, all the expense ! The new floor lamp, the rug, the clothes for Laura ! all for what? To entertain some other girl's fiancé ! Go to the movies, go ! Don't think about us, a mother deserted, an unmarried sister who's crippled and has no job ! Don't let anything interfere with your selfish pleasure I just go, go, go - to the movies !