OP - I'll throw out a different perspective.

I don't see not wanting to use a credit card as a terribly destructive behavior - the fact that she is willfully avoiding going into debt is a plus.

Some folks like and do well with credit products; and others avoid them.

I would be much more worried if someone didn't care about the debt they were racking up; or were focused on the "prestige" which they perceived came with their new AmEx card.

IME, I think you've got a winner on your hands. 

And when it comes to relationships, you can always be the one to manage and use revolving accounts. 

I didn't use CC's for a long time and DH says I was a pretty good catch.  At this point, in our house, I manage a good deal of the finances (and they're in pretty darn good shape).  DH uses revolvers but it's only for predetermined and prebudgeted items.  So we get the rewards, but I basically manage the cards.

And to answer your question, for me it would be high debt-load and blatant consumerism (whether they could afford it or not - it's just a major turnoff to me).