I have just spent a few days accompanied by a young lady who was about 40 years younger than me on a trip to the Canary Islands. Nobody gave us a second glance in all of the restaurants we were in, or on the bus tour we did. Really, I don't think this is an issue. It helped that she dressed in clothes that did not draw attention. I had a previous companion in Italy who wore more flamboyant outfits and that did attract some interest.