Ok so depending on floor colours and overall look that she is going for I think (if she is really adamant) that the blue could work if you change the Amaro cabinets to a whiter shade - this will give it an overall crisp, oceanside feel with the warmth of the soft walnut. Otherwise I would contrast it more with a mid-tone colour splashback in grey/brown tones. Again this totally depends of her tastes... Here's a photo that you could show her with the blue splashback - granted it is a little deeper than her selection but at least she can see it on a realistic scale and of course the timber/white cabinets are flipped in this one. Hope some of that helps!

Looks great from what is shown, but could you post a photo showing the whole kitchen please? I am having the same dilemma and very keen to see more of your tiles.

okay!!! A lot of these commenters obviously thought what I did - that the cupboards are a deep browney grey!! I think the responses would have been very different if we knew the cupboards were white. If you re-read thru the responses you will see that. Perhaps try re-posting the dilemma with a better pic. One of those original tiles may actually look ok.

The tiles from Johnson in the UK are stunning. It appears they only come in large 30x30 ? I was thinking of doing some sort of tile art just in the middle of the backsplash with the rest just plain offwhite tile. However, with this large 30x30 art work, the background tile would have to be cut to size to fit the area I have and might look too choppy???