We were staying with a total of two people for 6 nights and had a great time.
Bermeo is not really touristic, so very authentic! There are beautiful beaches close by (best accessible by car or bus) and the landscape is spectacular.
Ainhoa was really helpful for all questions and always repeated promptly, we had a personal check-in which I always appreciate.
The apartment is spacious (just be careful to not bump your head if you are over 1.90m high ;)) and for 2 people absolutely well equipped.