If this related to varocois veins, blood supply, bad knees, swollen ankles, arthritis, low table tops - well I could sort understand - but as for the cards you get ... Im sorry - Your probable outcome reflected by the cards are not relatively chnaged by your leg being crossed or uncrossed!
But now this seed has been planted within your consciousness, you may have the feeling or the idea that the cards cannot be correct unless you take up this position. I would ask questions of this reader now. What is the basis of her suggestion, and what relevance does it have to you - ask questions and ask why!!
Crossing legs can be like folding arms - but this is a reflection of protection and defensiveness - if this is in relation to body language - she may have just been asking you to uncross your legs to be open to ideas and consider all aspects before making decisions - it may have had nothing to do with the cards.
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Somehow this post is sounding really weird *
Even if she gives you her opinion on this 'leg-uncrossing' research it, and see what you think about it yourself - otherwise you may find that this 'suggestion' becomes a block within itself.
Just some thoughts
Blessings Elven x