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135-140 is already medium, the sear is going to take it way past medium. Why not just cook it direct and pull it at 135 and let rest? You can always put a piece for your wife back on the egg and let her portion go as far past medium as she likes.
Do not be fooled. The mini is a cooking machine. While it does have a small grid space, it can cook for hours on end on a handful of lump. Many of the pics from the first Spring Chicken movie is my mini (the one with the green marble table top). I recently bought a MM just for fun, but when I realized it was too heavy to travel around with, I sold it. Now, it's back to the mini for me.