Would it be possible that she purchased the credit card, as suggested, to prepare to disappear, but then thought it through and realized that her activities could be followed? Or that she got rid of the credit card to throw people off? In the documentary, they do discuss the fact that she's very bright, and may have been capable of planning her disappearance to the level that it could escalate to the point that it has.
Though I'm not by any means informed on either case, this does bear some similarities (perhaps insignificant) to that of Shannon Burgess, who was last seen November 27th 2014. LE has announced that she may be in Calgary, Edmonton, Vancouver, or Toronto.