Thank you for that additional information, the pictures and the measurements (cute ruler ;)
I doubt, given what you have posted, that this lesion represents something terrible like a melanoma.
But, the bot***** *****ne?
While I truly believe everything is OK and no intervention is necessary, It would be a simple thing to have her GP, or a dermatologist, remove the lesion completely. This way you and your wife would know exactly what the mole is and it would be gone.
Here, in the USA, you could schedule this minor surgery with a phone call -- I've heard it is harder to set this sort of thing up in the UK :(
Does this make sense to you?
It's safe for you to press the positive feedback button now if you so desire. And, never fear, even after you press that button I'll still be right here to continue helping you, but, as I do work for tips, I want to make sure you are happy before rating me.
Dr. Rick MD FACS