Sorry to hear that. My feet often gets blisters too no matter what kind of shoes I wear.
But from the picture, I think the shoe is too small for you. Last time, I bought a pair of flats from a shop, the SA suggested that I choose one size bigger for covered shoes to have some room for my toes, and its true. I feel so much more comfortable wearing it.
I have another method but not sure if it works for you. I would apply some petroleum jelly on the back of my feet and also on the portion of the shoe where its causing blisters, rubbed it in to soften the shoe. But do not apply too much as it can be slippery.