It annoys me that she's lying to her sons - she knows what it's like to be lied to, and now she's doing the same to them. They've already caught her out about the house ownership. However, this does happen - I know of a case where two adult sons have never been told about their mother's real parentage and who their actual grandparents were, although others in the wider family (me, for instance) do know the truth.
Re the interior decor: it seems OK to me. In the 50s, most of our walls were porridge coloured or with pale patterned wallpaper, but the (rarely-used) sitting room had one wall in a dark green wallpaper with a pattern of gold and white dots on it. It was expensive paper so my parents bought half a roll, just enough to do the alcoves either side of the chimney breast. Then about 1960 they papered the wall at the side of the staircase in a bold terra-cotta paper with a leaf pattern on it. Oh, and in the kitchen, one wall had a weird dark grey paper with pictures of kitchen utensils all over it. We were not posh, this was just a three-bed red brick semi built after the war. I do wish I had colour photos of all this, but of course it wasn't possible then.